JPH02268405A - Manufacture of ferrite magnet - Google Patents

Abstract

PURPOSE:To efficiently generate liquid state in a grain boundary, and to obtain a ferrite magnet having excellent coercive force by unitizing three types of melted materials such as SiO2-CaO-Al2O3 in which weight ratio is specified. CONSTITUTION:After powders of 62-73% of SiO2, 15-26% of CaO and 7-17%of Al2O3 by weight are mixed or pulverized, they are granulated, melted at 1170 deg.C in the atmosphere, and the melted material is temporarily left standing until it is used as an additive. On the other hand, Fe2O3 and BaCO3 or SiCO3 material are so mixed by a normal method that molar ratio Fe2O3/(SiO or BaO) become 4.0-6.0, temporarily baked to M phase, and the previously melted material is added 0.06-3% by weight to the temporarily baked material. Thereafter, it is normally pulverized, molded, sintered to form a ferrite magnet. Thus, a SiO.6Fe2O3 and BaO.6Fe3O3 sintered magnet having a magnet plumbite type structure (M state) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is an Sr0.6Fe203 magnet having a brambite structure (M phase) known as a ferrite magnet.
The present invention relates to a method for manufacturing a sintered magnet of the B a O.6 Fe 20 a system.

(Prior art) S r O is added to the structure known as a ferrite magnet.
-6F e 20 s, B a O・6 Fe
There are solid solutions of these, such as 203 (also written as MO.6Fe203). The method for producing these materials is to mix the raw material powders, granulate them, then perform a reaction process called calcination to form the M phase, pulverize them into calcined powder, and perform sintering. The final magnet product is then polished.

If the calcined powder is press-molded while applying a magnetic field, it will become an anisotropic magnet, and if no magnetic field is applied, it will become an isotropic magnet. Magnet performance includes maximum energy product (BH), residual magnetic flux density (B), coercive force +1aX
r(H), etc.

Furthermore, in the production of ferrite magnets, methods have been known that utilize various elements as trace additives. Specifically, SiO2S10 suppresses grain growth.
2IA, C “203, CaO that promotes sintering and smooths grain boundaries.

Examples include B l 203 r B203 and Al2O3 which is dissolved in the M phase matrix to change the anisotropic magnetic field constant.

Furthermore, by controlling the molar ratio of Fe2O3/MO, excess MO that deviates from the stoichiometric composition of 6.0 can be removed.
It is also common practice to control the sintered structure by enriching grain boundaries.

By the way, in Japanese Patent Application Laid-Open No. 48-91598, MO-
S t O-B O-CaO-Al120a2
By using a 2.3 type low melting point substance as an additive, we have succeeded in controlling the liquid phase at the grain boundaries and obtaining a magnet with less magnetic variation.

(Problems to be Solved by the Invention) However, since the method proposed in JP-A-48-91598 uses the same MO as the matrix, it is easy to dissolve and diffuse into the matrix of low melting point substances, resulting in crystal grains. The effect of the liquid phase in the magnetic field is insufficient, and no fundamental improvement has been achieved in magnetic properties, especially coercive force.

In view of this point, the present invention provides SiO-
To provide a method for manufacturing a ferrite magnet having excellent coercive force by effectively generating a liquid phase at grain boundaries by using a melt-treated product of 31Ei of CaO-A fl 20 a. .

(Means for Solving the Problems) In the present invention, when manufacturing a ferrite magnet, the weight ratio of S 102: 82 to 78% and CaO: 15 to 78% is determined in advance.
26%, AI! 203: A ferrite with excellent magnetic performance characterized by preparing a melt-treated 3N mixture of 7-17% and adding this melt-treated product to a ferrite calcined product in an iut ratio of 0.05-3%. This is a method for manufacturing magnets.

The present invention generates a small amount of liquid phase at the grain boundaries during sintering to promote the sintering reaction, and at the same time, smooths the grain boundaries to prevent the generation of reversed magnetic domains, thereby achieving high stability. The reason lies in the development of magnetic ferrite magnets. In addition, by controlling the amount of liquid phase generated by the amount of the melted material added in advance, the effect of the liquid phase can be controlled by the effects of other known additives, such as grain growth pinning, sintering promotion, and anisotropy. It has the characteristic that it can be extracted independently from effects on magnetic field constants, etc.

Hereinafter, the content of the present invention will be explained in detail.

First, 5IO2 powder, CaC0 powder, A4! 20 Prepare flour. Weigh each of these to obtain SiO□:
82-73%, CaO:L5-20%, AI20a
: Mix to achieve a balance of 7-17%.

The prepared powder is mixed or pulverized with a mixer, and then either as it is or granulated, and then melted in the atmosphere at a temperature of 1170° C. or higher.

If not melted, 5ly2. The components of CaO and Al2O2 remain separated as individual particles, and when sintering a ferrite magnet, the effect as a low melting point substance cannot be brought out. This melted product is temporarily stored for - hours until it is used as an additive.

On the other hand, Fe2O3 and B a COa or 5rCO raw materials are mixed in a molar ratio F e 20 s / (S r
00 "Bao) is mixed at about -4.0 to 6.0, M
Perform calcination to phase. To this calcined product, 0.05 to 3% by weight of the above melted product is added.

If this melt-processed product is less than 0.05%, the effect will be small, and if it is more than 3%, the magnetic properties will deteriorate due to the amount of non-magnetic material present, so the content should be 0.05 to 3%. After this, it is subjected to normal pulverization, then molded and sintered to form a ferrite magnet.

In addition, known additives, for example, 5IO2°AN203.
The effect of the present invention is not impaired even if Cr2O3, CaO, Bi2O2°B2O3, etc. are added alone or in combination without performing a prior melting process. These may be added either before calcination or before molding.

(Example-1) Fe203 and B a CO3 raw materials at molar ratio Fe2O3/
Mix so that BaO is 5.9, granulate, and then 13
After performing soaking calcination at 00℃ for 2 hours in air atmosphere,
A mixture prepared in advance as shown in Table 1 was melt-treated to prepare one with 0.8% additive and one with no additive. 1.1
2- was dry-pulverized, and this was dry-molded without a magnetic field.

Table (vt%) 70% 18% 12% 1250℃
This was soaked for 30 minutes at 1180°C for sintering in an air atmosphere.

Examples of the obtained magnet properties are shown in Table 2.

As can be seen from Table 2, magnets with particularly excellent coercive force were obtained when additives obtained by melt-processing the mixture of components shown in Table 1 were used.

Table 2 BHB laX r (MGOe) (KG) No additives 0.89 2.13 Melt processed material additives 1.12 2.32c (KOe) 2.77 3.58 (Example-2) Fe O and BaC0 raw materials were mixed so that the molar ratio Fe203/BaO was 5.8, granulated, and then 13
After performing soaking calcination at 00℃ for 2 hours in air atmosphere,
Add 0 to 5% of a melt-treated mixture shown in Table 3 prepared in advance, and add 0.3% of each of S io 2 and Ca COa in ffi amount ratio.
．． It was dry-pulverized to 98 tEa, and then subjected to dry-type molding without a magnetic field.

Table 3 (vt%) 67%
20% 13% 1250°C x 3h "This was soaked and sintered at 1200°C for 1 hour in an air atmosphere.

An example of the obtained magnetic properties is shown in FIG.

As can be seen from FIG. 1, magnets with particularly excellent coercive force were obtained when the weight ratio of the additive was 0.05 to 3% by melt processing the mixture of components shown in Table 3.

(Example-3) Fe O and S r COa raw materials at molar ratio Fe 20
Blend so that a/SrO is 5.8, and
S x 02.

0.5% each of Ca C03 and Aj7203.

The mixture of 0.6% and 177% additions 1,7, 13
00℃.

After performing calcination for 2 hours, 0.3% of a mixture prepared in advance having the components shown in Table 3 was melted at 1300°C for 1 hour and added 1. We make additive-free products,
Next, it was ground to 0.7 mm and subjected to wet magnetic field molding.

Table 4 shows the results of magnetic properties obtained by sintering this at 1190° C. for 30 minutes.

, / 810 Ca O, AI 203 quantity balance is 2
It can be seen that the sintering performance does not improve unless it falls within the scope of the present invention.

(Effects of the Invention) According to the present invention, a high-performance ferrite magnet with high coercive force can be obtained.

[Brief explanation of drawings]

FIG. 1 is a chart showing the amount of additives of the present invention and their effect on magnetism. agent

Claims (1)

[Claims] When manufacturing ferrite magnets, the weight ratio of S
iO_2: 62-73%, CaO: 15-26%, Al
_2O_3: A 3-component mixture of 7 to 17% is prepared by melting, and this melted product is added to a ferrite calcined product in a weight ratio of 0.05 to 3%. Method of manufacturing ferrite magnets.