JPH02271923A - Production of raw material oxide for ferrite - Google Patents

Abstract

PURPOSE:To reduce residual chlorine by mixing chlorides of metals which compose a ferrite, oxidation calcining this mixture to obtain an oxide mixture and then heating at a specified temp. CONSTITUTION:The metals used are Fe, Mn, Ni, Cu, Zn, Mg, etc., depending on the types of ferrite. For example, when Fe and Mn are used, aqueous solutions of FeCl2 and MnCl2 are mixed by a specified molar ratio, calcined with spraying at about 800 deg.C to obtain an oxide mixture of Fe2O3/Mn2O3 with about 75.3/24.7 weight ratio. This mixture is heated in air at 600-1000 deg.C for 40 minutes to reduce the residual chlorine to 500ppm or below. Then ZnO is added to the mixture by the weight ratio Fe2O3/Mn2O3/ZnO of about 69.4/22.8/7.8, and source materials of Ca and Si are added so that the mixture contains CaO and SiO2 by 500 and 200ppm, respectively, after sintered. They are mixed and processed into powder of 0.9-1.3mum particle size to obtain the raw material oxide for ferrite.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a raw material oxide for ferrite.

<Prior Art> The oxidative roasting of iron chloride to obtain iron oxide as a raw material for ferrite is widely practiced commercially, with spray roasting of pickling waste liquid from steel plates, etc., as a typical method. However, the iron oxide obtained usually contains 0.1 to 0.4% by weight of chlorine. These residual chlorine floats freely during the ferrite manufacturing process, particularly during core firing, and has harmful effects such as promoting corrosion and deterioration of equipment such as firing furnaces and causing abnormal grain growth of ferrite.

Therefore, various proposals have been made so far regarding its reduction.

Examples include: (1) A method in which the reaction product is retained in the lower part of the roasting furnace and air is blown into it (Japanese Patent Application Laid-open No. 116393/1983).

■ A method in which the produced iron oxide particles are crushed at 265°C or higher and held for a certain period of time under retained heat (Japanese Patent Publication No. 1988-880)
.

(2) A method of adding ammonium bicarbonate when mixing raw material oxides for ferrite (Japanese Patent Publication No. 54-5117).

■ Method of heating iron oxide under reduced pressure (Japanese Unexamined Patent Publication No. 61-14
(No. 6719) ■ A method of washing iron oxide with pure water.

etc.

All of these methods target iron oxide, but in order to obtain a sufficiently uniform mixing and dispersion of iron oxide and other metal oxides during ferrite production, grain growth by sintering iron oxide during dechlorination treatment is necessary. It is undesirable for this to occur, and ■,■
, (2) are all processed at a low temperature of 500° C. or lower. By the way, a report on the detailed investigation of the dechlorination behavior of iron oxide is published in the journal Th? of the Chemical Society of Japan. (1984)
1202, but according to this, treatment at temperatures below 500°C, where grain growth of iron oxide does not occur, has poor dechlorination efficiency and the normal amount of residual chlorine of 0.1 to 0.2 wt% is reduced to 500°C.
It is clear that it would take a long time of 4.5 degrees or more to achieve the following. In other words, in the case of dechlorination treatment of iron oxide alone, it is necessary to maintain the particle size of the powder in the submicron range of 0.5 to 0.7 n or less in order to obtain sufficiently uniform mixing and dispersion with other metal oxides. Therefore, the efficiency of dechlorination treatment was poor, and it was difficult to reduce the level of chlorine to a sufficiently low level.

In addition, the method (■) requires the addition of unnecessary additives for ferrite production, and the method (■) requires a large-capacity exhaust system to create a low vacuum for fine particles that originally have a large amount of surface-adsorbed gas. method (2) requires the use of pure water and requires additional energy for drying after washing, which increases costs. .

By the way, the normal manufacturing method for ferrite is to mix the metal oxides or carbonates that make up ferrite in a predetermined molar ratio, and then to make ferrite by calcining, crushing, molding, and firing. It has problems such as non-uniformity of composition and contamination of impurities during manufacturing.

In order to improve these problems, it has been proposed in Japanese Patent Publication No. 11550/1983 to use a mixed oxide obtained by roasting mixed chlorides as a raw material for ferrite, but in this case as well, the 0.1 to 0 in the oxides
．． This mixed oxide, obtained by conventional oxidative roasting at 600-850"C, has a particle size of 0.8n.
The characteristics of this proposal (if the calcination step, which is the batter) is omitted, a sufficiently high press density cannot be obtained during core press forming, and as a result, the shrinkage due to sintering during firing is large and the dimensional accuracy of the final product is reduced. In addition to being difficult to obtain, the presence of fine powder tends to cause abnormal grain growth.

<Problems to be Solved by the Invention> An object of the present invention is to provide a method for producing a raw material oxide for ferrite that makes it possible to remove harmful chlorine and maintains a particle size within a range suitable for press molding. .

As a result of repeated experiments to solve the above problems, we found that a mixed chloride containing the main metal elements constituting ferrite, such as P8, and one or more other elements such as Mn and Mg. is skewered, oxidized and roasted to form a mixed oxide, and then heated to a temperature range of 600 to 1000°C to efficiently reduce the amount of residual chlorine to 500°C or less and to reduce the amount of particle It has been found that the diameter can be adjusted to 0.9 to 1.3 H, which is optimal for press molding. By applying this to a raw material for producing ferrite, it was possible to stably produce a ferrite core with low shrinkage during firing and excellent magnetic properties.

Effect> First, the newly obtained knowledge that formed the basis of the present invention will be described in detail using experimental examples.

After mixing chloride aqueous solution of 1 g of FeC and 1 t of MnC at a predetermined molar ratio, spray roasting at 800°C produces a mixed oxide j
24.7 (weight% ratio), and the amount of residual chlorine is 301
〇-1 average particle size (by air permeation method) was 0.74 μm.

Figure 1 shows the change in the amount of residual chlorine after heating this mixed oxide to a temperature range of 500 to 1000°C and holding it in an air stream for 40 minutes.
It can be seen that when the temperature becomes 0 or less, especially when it exceeds 800°C, it becomes an extremely low level of 50-.

The black circle at 610°C shows that dechlorination is further promoted when water vapor is added to the air stream to adjust the dew point.

Next, FIG. 2 shows the mixed oxide as received without dechlorination heat treatment, and the mixed oxide that was heated to 500 to 1000°C and dechlorinated, and 8.0% by weight of ZnO and a small amount of 510! lCa1
After adding J1, mix, dry, and dry for 10 minutes using an attritor.
Granulation (PVA addition) is carried out, and then the outer diameter is 35 m5 at a molding pressure of It/cd. The numbers in parentheses in Figure 0, which shows the relationship between the compacting density when press-molded into a toroidal core with an inner diameter of 24 m and the average particle diameter after mixing the attritor, represent the heat treatment temperature.

The compacting density has an average particle size of 1.0 to 1.2. highest in n,
It can be seen that the density decreases even if the particle size is larger or smaller than this.If we look at the treatment temperature, the average particle size is 0.8 degrees or less for the material as it is and the material treated at 500℃. It can be seen that the corresponding molded density is 2.81 g/c- or less, whereas when the processing temperature is 600° C. or higher, the molded density becomes a sufficiently high level of 2.87 g/cd or more.

On the other hand, when FezO3 is used alone as a ferrite raw material as in the past, in order to ensure uniform mixing with Mn oxide, FeO 0. However, when applying the present invention, for example, in the case of a mixed oxide of Fe and Mn, FezO3 and MIDOs are already uniformly mixed and dispersed as fine particles in the receiving state. Therefore, even if dechlorination is performed at high temperatures to cause grain growth, it will not affect the uniform mixing of the constituent oxides.
Furthermore, it has been found that high molding density can be obtained during press molding.

Figure 3 shows that when a toroidal core made of the 800°C treated material mentioned above was heated in the air using the heat pattern shown in the figure, samples were pulled out at each temperature along the way and the phase ratio was determined by X-ray diffraction. These are the results of measuring changes in . From this figure, F
e, 0. and the change of Mn*Os to spinel phase is 100
While the temperature gradually increases to over 0°C, Zn
It can be seen that O disappears at 650°C and changes to other phases. This means that in the production of ferrite, it is important to ensure the uniformity of the mixing of the oxides of the ferrite constituent elements, and in the above example, it is important to mix the oxides of the main metals that make up the ferrite, Fe and Mn. ing. In this case it is important to mix the chloride of Fe(!:Mn), and Zn can be added in the form of ZnO in the final mixing step.

In the present invention, it is only necessary to mix in advance only the chlorides of the main metals constituting the ferrite.

Therefore, depending on the type of ferrite, Fe, Mn+Nl
+Cu+ Zn+ "g etc. are the main metals.

For example, the main elements constituting ferrite are Fe1 Mn+
In the case of three types of M, it is necessary to oxidize and roast these mixed chlorides.

The method of oxidizing and roasting the mixed chlorides of the wood invention is not particularly limited, but the spray roasting method, which is commonly used in the treatment of hydrochloric acid pickling waste for steel products, is preferred from an economical point of view.

The treatment that forms the core of the present invention is carried out at a temperature range of 600 to 1000°C, but as is clear from the above, this temperature range is limited to 600°C in order to reduce the amount of residual chlorine to a low level of 500°C or less. ℃ or higher is required. Also, 1
If the temperature exceeds 1,000°C, processing costs will increase and pulverization will be required after processing, so the temperature was limited to 1,000°C or less. The atmosphere during the treatment may be an inert gas such as nitrogen, but air is also sufficient. In addition, in order to increase the dechlorination efficiency, it is recommended to humidify with steam. If thermal efficiency is important in the treatment of the present invention, continuous treatment may be performed, for example, by connecting a rotary kiln or the like continuously to the outlet of the spray roasting furnace. For example, about 500
The heat possessed by the produced oxide itself, which is around ℃, can be used, making it possible to reduce the energy required for heating.

Next, the present invention will be explained in more detail based on Examples.

<Examples> Example 1 Aqueous solutions of FeCh and MnCZg were mixed at a predetermined molar ratio, and then spray roasted at 800°C. The resulting oxide composition was Fezes: Hn*Os -75,3: 24.7
(wt% ratio), the amount of residual chlorine was 3010-0
Next, FIG. 1 shows the change in the amount of residual chlorine when this mixed oxide was heated in an air stream for 40 minutes at a temperature range of 500 to 1000°C.

Next, a predetermined amount of ZnO is added to this dechlorinated oxide and Cab contained after firing, 510! Calculated by adding Ca and st sources at 500.20 Orpm each,
MnzO3: Zn0-69.4: 22.8:
7.8 (wt% ratio), press-molded into a toroidal core without calcining or pulverization, and firing a sample with the molding density shown in Figure 2 at 1330'C for 3 hours. Fig. 4 shows the average particle size of the powder before press molding along with the iron value. This firing resulted in a density after firing of 4.81 to 4.94 g/cd, but the volumetric shrinkage rate varied depending on the density of the molded material after pressing. Volume shrinkage rate is 42%
It showed a small value as below. Also, the receiver is left in place and 50
The material treated at 0° C. showed significant abnormal grain growth, whereas the material treated according to the present invention had a uniform normal grain structure. Although the reason for the above-mentioned abnormal grains and weave is not completely clear, it is thought to be due to the presence of a high level of residual chlorine and fine powder.

In addition, the magnetic properties of the sintered core are 100kHz 200mT
The iron shell value was evaluated by measurement, and it can be seen that very excellent values can be obtained by the treatment of the present invention.

Example 2 A mixed chloride containing predetermined amounts of Fe, Mn, and Mg was spray roasted to produce Vetos: MnzOs: MgO=8
A mixed oxide having a composition of 0.4:5.8:13.8 (wt% ratio) was obtained. The amount of residual chlorine is 2430. , the average particle size was 0.69 pm. After treatment according to the invention at 850'C for 30 minutes, 13.7% by weight of ZnO and Cab after sintering using an attritor.

CaC1 equivalent to 1500 and 1300- in Sing
z and SIO.

After the treatment according to the present invention, the average particle size was 1.13 μm and the amount of residual chlorine was 75 μm. Subsequently, after drying and granulation, it is formed into a toroidal core and heated at 1300'C.
Firing was performed for 2 hours. At this time, the molding density is 2 for the treated material.
．． 70 g/c-, and 2.58 g/c- when the material with the receiver in place was used as a comparison material, and the volume shrinkage was 42% and 45%, respectively. The initial magnetic permeability of jA-bound cocoa was 410 for the present invention material and 290 for the comparative material, indicating that the present invention material was superior.

<Effects of the Invention> As is clear from the foregoing, by applying the treatment of the present invention to the mixed oxide obtained by oxidative roasting of the mixed chloride of the main metal elements constituting ferrite, it is possible to eliminate harmful substances in subsequent processes. It is possible to efficiently reduce the amount of residual chlorine, and at the same time, it is possible to obtain a powder particle size that allows a sufficiently high compact density to be obtained without special calcination and pulverization processes, and through these factors, the volume shrinkage rate during firing can be improved. This has the effect of stably producing ferrite cores with low dimensional accuracy and excellent magnetic properties.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between heating temperature and residual chlorine amount.
Figure 2 is a graph showing the relationship between the average particle size of the oxide raw material and compacted density after heat treatment, Figure 3 is a graph showing the change in phase ratio during heating during ferrite core firing, and Figure 4 is , is a graph showing the relationship between the average particle diameter after heat treatment and the volumetric shrinkage rate during firing. Figure 1 Processing temperature ("C)

Claims (1)

[Claims] It is characterized by mixing the main metal elements constituting ferrite in the form of chlorides, then performing oxidative roasting treatment to form an oxide mixture, and then heating the mixture to a temperature range of 600 to 1000°C. A method for producing a raw material oxide for ferrite.