JPH10265272A - Production of ferrite magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To considerably shorten the time required to pulverize calcined powder by adding a specified amt. of a water-soluble carbonate and/or a COOH-contg. salt to a mixture of the calcined powder with a solvent and carrying out wet pulverization when the mixture is wet-pulverized, molded and sintered to obtain a ferrite magnet. SOLUTION: A water-soluble carbonate such as sodium carbonate and/or a COOH-contg. salt such as ammonium polycarboxylate is added by <=1 wt.%, preferably 0.4-0.8 wt.% to a mixture of stock powder such as calcined powder obtd. by calcining an SrCO3 -Fe2 O3 mixture with a solvent such as water, and wet pulverization is carried out. The powder-solvent mixture may be wet- pulverized in gaseous CO2 or gas contg. gaseous CO2 . The time required to pulverize the powder can be shortened by 30-50% as compared with the conventional method and the objective low-cost ferrite magnets having high performance are stably mass-produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ferrite magnet, which comprises adding a specific additive to a mixture of a calcined powder and a solvent and then subjecting the mixture to wet pulverization or mixing the mixture in a specific atmosphere. The present invention relates to a method for producing an inexpensive and high-performance ferrite magnet by greatly reducing the pulverization time by performing wet pulverization in a medium.

[0002]

_2. Description of the Related Art Magnetoplumbite-type hexagonal ferrite (hereinafter referred to as M-type ferrite) which is an oxide magnet material represented by SrO.6Fe ₂ O ₃ , so-called M-type ferrite, is disclosed in Philips, J. J. Went
Since their proposal, they have been mass-produced today due to their excellent magnetic properties and cost performance, and have been used in various fields.

In recent years, the weight of automobile bodies has been reduced in order to realize low fuel consumption of automobiles due to environmental problems. In order to reduce the size and weight of electrical components correspondingly, the size of ferrite magnets, which are the main component of the automobile, has been reduced. There is a strong demand for higher performance.

Conventionally, as means for improving the performance of ferrite magnets, the crystal grain size after sintering has been reduced by reducing the crystal grain size of the calcined powder to a single magnetic domain size. It is known to improve magnetic properties, especially coercivity.

[0005]

However, in order to reduce the size of crystal grains, it is necessary to carry out long-time fine pulverization using a pulverizer such as a ball mill or an attritor. For this reason, the production efficiency is reduced and the life of the crusher is shortened, resulting in an increase in cost.

In addition, when the grinding time becomes longer, the amount of the ultrafine particles increases, so that the dewatering property at the time of press molding is deteriorated, and the press efficiency is deteriorated and the molding machine is broken down.

On the other hand, as another means for improving the performance, SrO—Fe ₂ O ₃ , which is a main component of M-type ferrite, is replaced with SrO-M
eO-Fe ₂ O ₃ (Me is Co, Zn, a metal ion of 2 values such as Fe) was extended to ternary, four with improved saturation magnetization (W type, X-type, Y-type, Z Ferromagnetic ferrite magnets having a complex hexagonal structure (type) have also been proposed.

However, in order to obtain satisfactory properties even in the above ferrite, the crystal grain size of the calcined powder must be as small as possible in the conventional M ferrite.
It is the same as mold ferrite, and has not yet solved the fundamental problem.

An object of the present invention is to solve the conventional problems and to provide a manufacturing method capable of significantly reducing the time required for fine pulverization and capable of stably mass-producing inexpensive and high-performance ferrite magnets. And

[0010]

The inventors of the present invention have conducted various studies on the pulverizability of ferrite powder in wet pulverization. As a result, when the powder after calcination is wet pulverized, a mixture of the powder and a solvent is added to the mixture. By adding a predetermined amount of a salt containing a water-soluble carbonate and COOH and then performing wet pulverization, or by wet pulverizing the mixture in carbon dioxide or a gas containing carbon dioxide, the time required for pulverization is reduced. It has been found that it can be reduced by 30% to 50% as compared with the related art.

That is, the present invention provides a method for producing a ferrite magnet in which a mixture of a calcined powder and a solvent is wet-milled, and then molded and sintered. And at least 1% by weight of a salt containing COOH and COOH, followed by wet pulverization.

Further, the present invention provides a method for manufacturing a ferrite magnet in which a mixture of a calcined powder and a solvent is wet-milled, and then molded and sintered, wherein the mixture of the raw material powder and the solvent is mixed with carbon dioxide or carbon dioxide. Is a method for producing a ferrite magnet, characterized in that the ferrite magnet is wet-milled in a gas containing

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the target ferrite magnet is SrO.6Fe ₂ O ₃ or BaO.6.
M type ferrite magnet represented by Fe ₂ O ₃ or S
A ferrite magnet having a known composition such as a W-type ferrite magnet represented by rO-MeO-Fe ₂ O ₃ (Me = binary metal ions such as Co, Zn, and Fe) can be used. A similar effect can be obtained with a ferrite magnet.

Further, in the present invention, known production methods for obtaining a calcined powder, a solvent to be added to the calcined powder, and a pulverizer for wet-milling a mixture of the calcined powder and the solvent are all known. Can be adopted. For example, water can be used as a solvent, and a ball mill, an attritor and the like can be used as a pulverizer.

According to the present invention, a mixture of the above-mentioned calcined powder and a solvent is added with 1% or less of a water-soluble carbonate and / or a salt containing COOH by 1% by weight or less, followed by wet pulverization. It is characterized in that the grinding time can be greatly reduced. Examples of the water-soluble carbonate include potassium carbonate, sodium carbonate, barium carbonate, ammonium hydrogencarbonate (ammonium bicarbonate), potassium hydrogencarbonate, sodium hydrogencarbonate, and the like. Ammonium carboxylate and the like can be used.

Each of the above additives can be used alone or in combination.
If it exceeds, the pulverizability is excessively improved. For example, in the case of M-type ferrite, the ferrite is partially decomposed into spinel and Sr carbonate or Ba carbonate, which is not preferable because magnetic properties are deteriorated. Therefore, the amount of addition is limited to 1 wt% or less. A particularly preferred addition amount is 0.4 to 0.8 wt%.

The present invention also provides a method of wet-milling a mixture of a calcined powder and a solvent in an atmosphere containing carbon dioxide gas, as in the case where the above-mentioned additives are added.
The pulverization time can be greatly reduced. The atmosphere containing carbon dioxide is preferably carbon dioxide, a mixed gas of carbon dioxide and other gases, or a mixed atmosphere of them and air.

In the case of a closed pulverizer such as a ball mill, when the mixture of the calcined powder and the solvent is charged into the pulverizer, the atmosphere is adjusted to the above-mentioned atmosphere. Or after the mixture has been charged into the crusher,
Means such as replacing the inside through the intake / exhaust port can be adopted.

In the case of an open type pulverizer such as an attritor, a means such as bubbling the slurry being pulverized with the above-mentioned gas or spraying a gas directly on the slurry can be employed. In addition, as long as the gas is positively injected, such as the above-described bubbling and direct gas blowing, air (containing a small amount of carbon dioxide) can be used.

By using the wet pulverization described above,
The time required for the pulverization can be significantly reduced to 30% to 50% as compared with the conventional method, so that the production efficiency can be improved and the life of the pulverizer can be prolonged. Since the amount of the ultrafine particles is extremely small, the dewatering property at the time of press molding is good, so that the press efficiency can be improved and the life of the molding machine can be extended.

The fine powder in the form of a slurry after the wet pulverization may be formed as it is as described above, or the slurry may be dried once to form a dry powder, and then formed using the dry powder.
Known molding means can be employed, and sintering after molding can be performed under known conditions.

[0022]

EXAMPLES Example 1 SrCO ₃ and Fe ₂ O ₃ were weighed at a molar ratio of 1: 5.9,
After mixing, the mixture was calcined in the atmosphere at 1300 ° C. for 1 hour to obtain a calcined powder. The calcined powder and water as a solvent were charged in a ball mill pot, and 0.8 wt% of sodium carbonate as a water-soluble carbonate was further added. Then, the ball mill was rotated to perform pulverization. FIG. 1 shows the relationship between the grinding time and the grinding particle size. The pulverized particle size was measured by BET.

Comparative Example 1 The same calcined powder as in Example 1 was used and pulverized under the same conditions as in Example 1 without adding sodium carbonate. FIG. 1 shows the relationship between the crushing time and the crushed particle size.

As is clear from FIG. 1, it can be seen that the wet pulverization according to the present invention to which a water-soluble carbonate is added significantly improves the pulverization efficiency as compared with the case where no water-soluble carbonate is added. For example, when the pulverized particle size is 0.05 μm, in the comparative example, pulverization must be performed for 34 hours, but according to the present invention, pulverization can be performed in 24 hours, and about 30 hours.
% Of the pulverization time can be reduced.

Example 2 Using the same calcined powder as in Example 1, sodium carbonate was reduced to 0,
Pulverization was performed under the same conditions as in Example 1 by adding 0.2, 0.4, and 0.8 wt%, respectively. FIG. 2 shows the relationship between the crushed particle size and the relative intensity value of the main peak (311) of spinel in the obtained fine powder.

As is clear from FIG. 2, the addition of 0.2 wt% slightly increases the spinel amount, and the addition of 0.4 wt%, 0.8 wt%
It can be seen that the amount of spinel increases as the addition amount increases to wt%. As described above, an increase in spinel is not preferable because it causes deterioration of magnetic properties. Therefore, in the present invention, the addition amount of the salt containing the water-soluble carbonate and COOH is 1% by weight or less, and more preferably 0.4 to 0.4%.
8 wt%.

FIG. 2 also shows that the amount of spinel increases as the grinding time increases and the grinding particle size decreases. Therefore, in particular, when the ground particle size is reduced, it is necessary to appropriately adjust the addition amount of the water-soluble carbonate and the salt containing COOH within a range of 1 wt% or less.

[0028]

According to the method for producing a ferrite magnet according to the present invention, the time required for wet pulverization is reduced by 30% to 5% compared with the conventional method.
Since it can be greatly reduced to 0%, the production efficiency can be drastically improved and the life of the crusher can be extended, which is a very effective production method for industrial production.

Further, according to the present invention, since the amount of ultrafine particles generated at the time of wet pulverization is extremely small, the dewatering property at the time of press molding is good, the press efficiency is improved, and the life of the molding machine is extended. As a result, a high-performance ferrite magnet can be provided at a low cost from a stable productivity improvement effect.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a pulverizing time and a pulverized particle size in Example 1 of the present invention.

FIG. 2 is a graph showing a relationship between a crushed particle size and a relative intensity value of a main peak (311) of spinel in crushed powder in Example 1 of the present invention.

Claims (2)

[Claims] 1. A method for producing a ferrite magnet in which a mixture of a calcined powder and a solvent is wet-pulverized and then molded and sintered, wherein the mixture of the raw material powder and the solvent contains a water-soluble carbonate and COOH. A method for producing a ferrite magnet, wherein one or two kinds of salts are added in an amount of 1 wt% or less, and then wet pulverization is performed. 2. A method for producing a ferrite magnet in which a mixture of a calcined powder and a solvent is finely pulverized after being wet-pulverized, and then the mixture of the raw material powder and the solvent is mixed with carbon dioxide or a gas containing carbon dioxide. A method for producing a ferrite magnet, comprising performing wet pulverization in a ferrite magnet.