KR0144224B1 - Soft ferrite raw material powder its sintered body and their production method and apparatus - Google Patents

Abstract

The present invention makes it easy to obtain a soft ferrite sintered body, for example, a sintered body having a crystal grain size of 2 μm or less by using an atomization roasting method and an average particle size of 0.1 μm or less and ultrafine powder obtained by atomization roasting as a raw material calcining powder. The present invention provides an apparatus capable of obtaining a soft ferrite raw material powder having a very small content, extremely small deviation of high vapor pressure components such as zinc between the atomized raw material solution and the oxide as a product, and which is sufficiently oxidized.

The present invention has excellent power loss characteristics in the high frequency band, in particular the MHz band, it is possible to economically produce a soft ferrite core very effective in reducing the size of the high frequency transformer. Even in the method for producing the soft ferrite raw powder, the variation of the recovered powder is extremely small, and residual hydrogen chloride and chloride can also be reduced. Therefore, the burden on the component adjustment step and the CI removal step after roasting can be reduced, and the process step can be shortened. Therefore, the present invention can significantly reduce manufacturing cost and improve quality.

Description

Soft ferrite powder, its sintered body, manufacturing method and apparatus

1 is a diagram showing the micro-deviation of the three main components (Fe-Mn-Zn) of the soft ferrite raw powder.

2 is a diagram showing the relationship between the effect of phosphorus content on the ferrite raw powder.

3 is a diagram showing the relationship between the effect of chromium content on the ferrite raw powder.

4 is a diagram showing the relationship between the grinding energy index of the soft ferrite raw material powder and its specific surface area according to the present invention.

5 is a diagram showing the relationship between the standard generated glass energy and the temperature of the reaction of metal chlorides with oxygen.

FIG. 6 is a diagram showing the relationship between standard generated glass energy and temperature of the reaction of metal chlorides with oxygen.

FIG. 7 is a diagram showing the relationship between standard generated glass energy and temperature of reactions with metal chlorides, oxygen and water.

8 is a diagram showing the relationship between the time from atomization roast to quench and the ZnO deviation in the liquid composition.

9 is a diagram showing the relationship between the mole fraction of H ₂ O or O _{2 in} a refrigerant and the mole fraction of Zn oxide in total Zn.

10 is a schematic diagram of an apparatus for practicing the present invention.

11 is a diagram showing the relationship between H ₂ O and O ₂ mole fractions and residual chlorine.

12 is a schematic cross-sectional view of an atomization furnace for producing a composite oxide ferrite powder according to the present invention.

13 is a diagram showing the relationship between the angle of the top and the average droplet diameter in roasting.

14 is a diagram showing power loss and saturation flux density of a soft ferrite core according to the present invention and the prior art, respectively.

* Explanation of symbols for main parts of the drawings

1: roaster 2: chiller nozzle

3: Passage 4: Chiller

5: Raw material spray nozzle 6: Center burner

7: extended slope part

The present invention relates to a soft ferrite raw material powder, its sintered body, and a manufacturing method and apparatus. More specifically, the present invention provides a method for directly preparing ferrite powder by atomizing and roasting a soft ferrite raw material powder, a ferrite sintered body thereof, and a solution containing chlorides of metal elements constituting the ferrite, and An apparatus used for the method and a method for producing a ferrite sintered body.

In recent years, as the size and weight of power transformers used to switch power supplies have been required, the driving frequency has been extended to the high frequency band beyond the conventional 100 KHz to 500 KHz range, and applications in the future MHz band are also being tested. However, because of eddy current loss proportional to the square of the driving frequency, which is a problem even during power loss, especially in the high frequency band, the power loss increases with increasing frequency, so that the heat generation cannot be ignored. In the past, various countermeasures have been proposed to solve these problems. Among them, some suggest that the soft ferrite sintered body has a fine structure such as small structure variation of individual grains, small amount of impurities, and high density, so that high performance can be expected by using the soft ferrite sintered body required to achieve such excellent characteristics. Doing.

In particular, since the crystal grain size of the sintered body is effective, Japanese Unexamined Patent Publication No. 1-224265 discloses a method of limiting power loss in the high frequency band by producing a sintered body having an average grain size of 5 탆. Another improved example of the use of fine powders prepared by hydrothermal synthesis as raw powder has been reported (see Nikkei Material Technology, 125 (1993) 24). The soft ferrite raw powder to obtain such a sintered compact should have a small amount of impurities, have a uniform composition, have a small variation in particle size distribution, and should be fine particles. Therefore, improvements and developments for this have been carried out steadily.

As one of the iron oxide methods of obtaining a soft ferrite raw material, a method of atomizing and pyrolyzing the pickling waste liquid of steel is known. In this case, when various metal ions constituting the ferrite are mixed in the pickling sap, the ferrite powder can be obtained by atomization and pyrolysis. However, according to the conventional atomization pyrolysis method, high vapor pressure components such as homogeneous compositions and zinc evaporates cannot be obtained very easily. Therefore, Japanese Unexamined Patent Publication (Kokai) No. 55-144421 discloses Fe-Mn in a predetermined composition by atomization pyrolysis (baking) after mixing Fe and Mn ions having stable high temperature pyrolysis characteristics as a soft ferrite sintered body in the form of an aqueous chloride solution. A method for producing a soft ferrite sintered body is disclosed in which a mixed oxide containing is prepared, followed by mixing zinc oxide powder, followed by pulverization, granulation, molding and sintering.

On the other hand, as a method for producing a composite oxide of a Zn-containing soft ferrite raw material powder, Japanese Unexamined Patent Publication No. 63-156017 discloses a chloride solution containing a ferrite raw material in a predetermined composition in a fluidized roasting furnace. A method is disclosed in which a powder is recovered by spraying with a decomposition product and then the soft ferrite raw material powder is collected by a dust collector.

As an improved method of the above-described Japanese Unexamined Patent Publication No. 63-156017, Japanese Unexamined Patent Publication No. 1-192708 discloses by mixing a high-temperature high-speed gas containing no reducing substance with a mixed solution of starting metal chlorides. A method is disclosed in which a metal chloride mixture is decomposed while rapidly maintaining a predetermined roasting temperature, while the starting material and the decomposed product are co-flowed together with a heat gas stream to flow.

In connection with the purification of the chloride solution, Japanese Unexamined Patent Publication No. 63-315522 discloses that an aqueous solution of iron chloride is contacted with a roasting gas generated during this process to perform thermal concentration and insolubilize the Si component in the iron chloride demand solution. A method is disclosed in which iron is added to this solution to consume free acid in the range of pH 1-3, insolubilizing most of the Al, Cr, Cu and P components in the solution to separate and remove insoluble materials.

However, according to the above-mentioned prior art, it is difficult to manufacture a sintered compact having a crystal grain size of 2 μm or less. In order to manufacture a sintered compact having such an ultrafine diameter, it has been required to sinter by HIP or hot press using the ultrafine powder produced by the hydrothermal method. However, when the powder produced by the hydrothermal method is used as a starting material, or when HIP and hot press are used as the sintering apparatus, the production cost is extremely high, and the mass-generating aspect still remains a problem that is not solved.

When producing complex oxide for soft ferrite raw powder, the method of high temperature oxidation reaction by spraying chloride solution into the fluidized roasting furnace is controlled. It is impossible, and the reaction time varies from several tens of seconds to several tens of minutes. Therefore, even if the particle size of the ferrite raw material powder and the microscopic homogeneity of the composition are improved, the problem of large particle size distribution and large component variation remains to be solved.

In the atomization roasting method according to the prior art, such as the spraying of starting materials, the particle size control and spraying of the soft ferrite raw material powder as a product and its components, except the conditions for roasting in a steam-containing oxidizing atmosphere, are sprayed. The quenching condition using the refrigerant containing H ₂ O` and / or O ₂ for the control of the reaction and the predetermined time was not confirmed. If these conditions are not established, pyrolysis and high temperature oxidation by atomization roasting become incomplete, and chlorination of undecomposed substances or reaction products leaves 1 to 3% of chloride. Evaporative scattering of zinc also occurs. Incomplete spray control also changes the particle size of the resulting oxidized powder. Therefore, these methods were not perfect as a method for producing Fe, Zn and Mn type soft ferrite raw powders.

The present invention is the most suitable for the latest type of high frequency transformer, raw material powder to solve the problems related to the production of soft ferrite raw material powder, which can produce a soft ferrite core (excellent uniformity) and particularly excellent power loss characteristics, An object is to provide a sintered body, a production method thereof, and an apparatus.

In order to solve the above problems, the present inventors have achieved this by testing the sintering conditions of the calcined raw powder and the molded article. That is, the present inventors sintered the powder at a normal pressure under a controlled sintering atmosphere at a temperature of 1,100 ° C. or less using ultra-fine powder having an average particle size of 0.1 μm or less, as measured by TEM observation, so that the crystal grain size was 2 μm or less. It has been found that very small soft ferrite sinters can be easily obtained. In addition, by sintering the powder at a temperature of 1,100 to 1,350 ° C, a soft ferrite sintered body having a uniform particle diameter ranging from 2 μm to several tens of microns can be produced. In addition, according to the present invention, the amount of H ₂ O and O ₂ is controlled within a predetermined range during atomization roasting, subjected to a sufficient oxidation reaction by carrying out rapid quenching after roasting, and the residual chlorine content is very small, and the evaporation of Zn There is also provided an atomization roasting method for obtaining soft ferrite powder with little scattering and a device therefor.

That is, according to the present invention, by the high temperature oxidation method, it is possible to mass-produce ultrafine soft ferrite raw material powder having high purity, high composition and uniform particle size as an essential condition for producing an ideal soft ferrite sintered body. The present invention also provides a method for producing a soft ferrite sintered body having high performance and necessary properties by using the raw material as it is or after adjusting the particle diameter to a predetermined diameter by a so-called build-up method. . Accordingly, the present invention provides necessary and sufficient conditions for the production of an ideal soft ferrite sintered body. That is, the present invention can achieve the microstructure control of the soft ferrite sintered body, which is difficult by the so-called break-down method according to the prior art, without using a special method such as HIP.

More specifically, the present invention, the ratio of Fe, Mn and Zn in the composition is 65 to 85% by weight when converted to Fe ₂ O ₃ for Fe, 10 to 30% by weight when converted to MnO in the case of Mn, and Zn In the case of, it is maintained at 2 to 25% by weight in terms of ZnO, and the content of P and Cr is soft ferrite raw powder produced by high temperature oxidation so as to be contained as a trace component satisfying the relationship of P≤20ppm and Cr≤50ppm Also provides. The present invention provides a sintered body obtained by performing normal pressure sintering on the above-described raw material, and a sintered body having an average grain size of 2 μm or less obtained by directly granulating and molding the raw material and sintering at a temperature of 1,100 ° C. or less. With regard to the preparation of such materials, the present invention defines the atmosphere as sintering conditions of the sintered body. Regarding the production of the raw powder, the present invention defines the conditions for atomizing and cooling the chloride to be sprayed, and also defines the trivalent iron ions and impurities contained in the starting chloride solution. In addition, with respect to the apparatus for producing these materials, the present invention improves the angle of the slope portion at the top of the roasting furnace and the treatment of the liquid spray nozzles and burners, and prevents the adsorption of solid materials.

Hereinafter, the best mode for carrying out the present invention will be described in detail. The ferrite manufacturing method according to the present invention was carried out by testing the sintering method of the raw material mixed powder by solid phase reaction from the viewpoint of the raw material powder described above, and the solution pyrolysis method by the liquid phase reaction. In the sintering process as a subsequent processing step, the properties of the raw powder exhibit a great influence, and in particular, the relationship between the average particle size and the sintering density is noteworthy. That is, when the average crystal size is small, the sintered density is increased by short time sintering and the subsequent change is small. If the chemical compositions of the powders are identical, their uniformity greatly affects the aspect of the sintering process and the magnetic properties of the ferrite core as a product. The present invention succeeded in achieving the uniformity of chemical composition and miniaturization of the average crystal size in the raw material powder by the powder production method.

FIG. 1 shows the micro-deviation of the three main components (Fe-Mn-Zn) of the soft ferrite raw material powder by grinding and mixing a predetermined amount of iron oxide, manganese oxide and zinc oxide powder. Figure 1 (a) shows the micro-deviation of the three main components (Fe-Mn-Zn) of the soft ferrite raw material powder according to the present invention, Figure 1 (b) shows the three main components (Fe) of the soft ferrite raw material powder according to the prior art Micro-deviation of -Mn-Zn). Each analytical sample was prepared by molding each powder sample into a disc shape, immersing it in a resin and then mirroring the copper surface. Every 0.16 μm was analyzed by X-ray microanalyzer scanning and computer-processed. The analysis results show that the deviation in the present invention is 1/7 to 1/6 of the prior art in Fe ₂ O ₃ , 1/10 to 1/4 of the prior art in MnO, and 1 / of the prior art in ZnO. It can be improved from 8 to 1/3. This result clearly demonstrates the uniformity of the soft ferrite raw material powder of the present invention. In addition, this soft ferrite raw powder is produced by a method which is far more mass-productive than the conventional method using the hydrothermal synthesis method.

Usually, the soft ferrite raw material powder uses Fe ₂ O ₃ , Mn ₃ O ₄ , and ZnO as main components, and SiO ₂ , CaO, and the like as _secondary components. These ingredients are mixed and ground and then calcined in the range of about 900 to about 1,100 ° C. to obtain a raw powder.

In order to obtain a soft ferrite raw material powder (so-called calcination powder) having a predetermined particle size, the calcined raw material powder is subjected to a long term treatment by a pulverizing / dispersing apparatus such as a ball mill after calcination, but this operation may lead to deterioration of the impurity mixture and the particle size distribution. There is a danger.

The particle size of the main and minor components of the raw powder ranges from several microns to several hundred microns.

The soft ferrite raw powder is 65 to 85% by weight when the ratio of Fe, Mn and Zn is converted to Fe ₂ O ₃ , 10 to 30% by weight when diffused as MnO, and 2 to 25% by weight when converted to ZnO. The composition deviation should be microscopically homogeneous, and the content of P and Cr as trace components should satisfy P≤20ppm and Cr≤50ppm. In order to test the effects of phosphorus, chromium and the like, a test was carried out using this ferrite raw powder as shown in FIGS. 2 and 3. 2 shows the relationship between ΔB and P content. Here, ΔB represents the difference between B ₁₀ (saturation flux density in external magnetic field of 10 Oe) and Br (residual flux density) in magnetic high lines, which indicates an acceptable magnetization range in switching power supply and the like. . 3 shows the relationship between Cr content and power loss for each P content. As a result, it was found that phosphorus must be limited to 20 ppm or less, and chromium must be limited to 50 ppm or less.

The reason why the particle size of the soft ferrite powder according to the present invention should be 0.1 μm or less will be described later.

The phenomena that occur with the sintering of raw powders are as follows in terms of particle size and composition and are well known in the art (see Electronic Material Series, Maruzen, 1986, 11. 30.).

If the crystal grain size of the sintered compact obtained by forming n powder particles having an average particle diameter d ₁ and a composition difference between the particles δ and sintering these powder particles is d ₂ , we can conclude that:

The compositional change between the sintered grains decreases to δ / (n) ^1/2 :

Provided that n = (d ₂ / d ₁ ) ³ .

In order to obtain a sintered compact having a smaller composition difference, the raw powder particle composition must be uniform and fine.

The finer the structure of the sintered body, the smaller the particle size of the raw material powder, which is also an essential condition for maintaining the performance of the ferrite sintered body.

It is also well known that the smaller the particle size of the raw material powder as the sintered body material, the higher the surface energy thereof and the higher the reactivity thereof.

However, if the reactivity is too high, bubbles are trapped in the crystal grains during the sintering reaction step, and a good sintered body cannot be obtained.

Especially in the case of soft ferrite raw powder, when the spinel structure is partially decomposed into hematite, the reactivity in this portion is increased. Therefore, the spinel conversion of the raw powder must be high. In the case of the soft ferrite raw material powder of the present invention having a particle size of 0.1 μm or less, spinel conversion of at least 95% is secured in terms of the peak area ratio of X-ray diffraction, and uniformity for micro sintering reaction is also maintained.

In view of the method for producing a ferrite sintered body as the second invention of the present invention, the average particle size of the calcined raw material powder is 0.1 μm or less, and under these conditions, the direct application of granulation molding as already described is also possible. It is another feature. When this sintered compact is obtained, a sintering temperature should be set to 1,100 degreeC or less for the following reason. When sintering is carried out at a temperature higher than this temperature, grain growth occurs, and the particle size of the sintered compact is over 2 μm. At elevated temperatures, the atmosphere is limited to a nitrogen atmosphere with an oxygen content of 100 ppm or less. If the oxygen content exceeds 100 ppm, a dense sintered body cannot be obtained, and in some cases, α-Fe ₂ O ₃ is produced and a ferrite single phase cannot be obtained.

A sintered compact having a crystal grain size of 2 to several tens of microns can be obtained by sintering a raw powder having a particle size of 0.1 μm or less at 1,100 to 1,350 ° C. while maintaining the sintering atmosphere as described above.

On the other hand, a sintered compact having a sintered density of at least 4.9 g / cm ³ and a crystal grain size of 2 to several tens of microns is also subjected to heat treatment at 200 to 900 ° C. to obtain so-called build-up particles, which are then ground and granulated in a known sintering atmosphere. It can be obtained by carrying out the forming and molding.

4 illustrates the grinding conditions of the soft ferrite raw material powder by plotting the grinding energy index in the abscissa in consideration of the processing time, the amount of balls for grinding the treated powder, and plotting the grinding result (specific surface area) in the ordinate. will be.

This diagram shows the adsorption method when the conventional soft relite raw material powder and the soft ferrite raw material powder according to the present invention are thermally grown at 200, 400, and 800 ° C. for particle growth, and then treated by a wet system dispersion apparatus for a predetermined time. Explain the change in particle size due to the specific surface area measured by

The particle size decreases over time (specific surface area becomes large), and the rate of change of the particle size far exceeds the specific filling amount of the grinding energy. This tendency is more noticeable in the soft ferrite raw powder according to the prior art method, and corresponds to the generation of ultra fine powder due to excessive grinding and poor particle size distribution. This fact reveals the limitation of the particle size control of the soft ferrite raw powder of the prior art using iron oxide, manganese oxide, and zinc oxide as the raw material by the so-called break-down method.

In contrast, the present invention easily increases the particle size required by the particle size control by the so-called build-up method, which is represented by the example of processing in a temperature range of 200 to 800 ° C. using a raw material powder of less than 0.1 μm as a base. You can.

The powder thus built up can be converted into a raw powder having a sharp particle size distribution by a short time treatment as a loose agglomerate. The input range of the grinding energy which does not lead to the occurrence of abnormal ultra fine powder is wide, and the desired soft ferrite raw powder can be easily produced.

That is, another feature of the present invention is that it is possible to provide a soft ferrite raw material powder having a sharp particle size distribution in a range comparable to a conventional calcined powder in a fine powder of less than 0.1 μm. .

In order to sinter the powder and obtain a sintered body having a high density, the following matters should be considered.

In order to increase densification rate with sintering, it is preferable that the particle size of the powder is small. However, if the powder is too fine, the molding density falls, and therefore, the sintered density also falls. On the contrary, when the particle size is too large, the sinterability is lowered even if the molding density is increased. Therefore, a sintered compact having a high density can be produced by considering both formability and sinterability.

If the particle size distribution is wide, the shrinkage ratio between the particles varies depending on the position of the particles, and the particles are rearranged to leave voids. As the neck grows, the approach speed of the center of the powder particles increases, at which time the particles become smaller due to volume diffusion and grain boundary diffusion.

If the heterogeneity of the chemical composition is present in the soft ferrite raw powder, the sintering speed during the sintering process is larger than the uniform part, and the sintering speed difference locally occurs. As a result, the shrinkage becomes non-uniform so that voids are formed. In addition, the microcrystalline structure of the sintered body is heterogeneous, and the electromagnetic properties also become poor. In some cases large voids are formed by the Kirkendall effect.

Conventional soft ferrite raw powders are prepared by mixing iron oxide, manganese oxide and zinc oxide, calcining the mixture at a high temperature of 900 to 1,100 DEG C, and then grinding the mixture. However, the sintering between the particles proceeds firmly from both sides of the high temperature sintering and the sintering between the particles between the different components, and a neck is formed which cannot be separated even by grinding.

In this case, during molding, a large gap is formed between the aggregated particles and remains even after sintering, thereby lowering the density of the sintered compact.

In the soft ferrite raw material powder and the soft ferrite raw material powder made from the powdery material according to the present invention, the uniformity of the individual particles and the uniformity among these particles are extremely high, so that the particle size distribution is narrow and sharp, thus forming a neck between the particles. This does not occur and independent particles are formed without aggregates. For this reason, these raw powders can form an extremely dense and extremely uniform sintered body without abnormal grain growth.

The HIP method can produce a dense sintered body close to the true density by low temperature sintering. In pressure-sintering, when pressure is applied to the branched powder, the driving force for densification can be increased by mechanisms such as rearrangement of particles, diffusion creep, plastic derivatization, and so on. Densification of can be achieved simultaneously by low temperature sintering application. However, if the soft ferrite raw material powder of the present invention is used and the particle size is optimally adjusted, a high density sintered body comparable to the HIP material can be easily obtained without applying the pressure required by the HIP method.

The production of soft ferrite raw powder by high temperature oxidation reaction (atomization roasting) of aqueous solutions of Fe, Mn and Zn chlorides according to the present invention is generally carried out through the following steps.

Atomization of the aqueous metal chloride solution into the roasting furnace and the high temperature oxidation reaction;

Coexistence of Fe—Mn—Zn tertiary metal oxide as a reaction product with a mixture of hydrogen chloride gas, steam, and the like;

Separation and Recovery of Ternary Metal Oxides Containing Fe—Mn—Zn from Hydrogen Chloride Gas.

In other words, it is necessary to separate the metal oxide and the hydrogen chloride gas under high temperature oxidation conditions that limit the residual chloride and limit the chlorination of the Fe-Mn-Zn tertiary metal oxide in the presence of hydrogen chloride.

The following schemes illustrate the decomposition and oxidation of O ₂ and / or H ₂ O from metal chlorides to metal oxides:

In the formula, M represents a divalent metal element such as Fe, Mn, Zn or the like.

5 shows the standard formation of the glass energy of reaction (a). This diagram facilitates the oxidation reaction of the acid chlorides of Schemes (6) and (7) in FIG. 5, which can be used to form high-purity iron oxide by oxidative roasting of iron chloride crystals in air on an industrial scale. Shows that it can.

In FIG. 5, equation (4) shows the possibility of manganese oxide formation by the roasting of manganese chloride in the air.

It is believed that the decomposition / oxidation reaction of the aqueous chloride solution can proceed according to schemes (b) and / or (c).

6 shows the standard formed glass energy of Scheme (b), demonstrating that oxidation of Fe, Mn, and Zn chlorides does not proceed easily only by steam. In comparison, in the reaction (b), oxidation of Fe chloride occurs most easily and Mn is most difficult to oxidize.

7 shows the standard formed glass energy of Scheme (C). This diagram shows that oxidation of Fe chloride proceeds easily and oxidation of Mn chloride proceeds more slowly than Fe. However, the oxidation of Mn chloride can proceed more easily in (c) than in (b).

In connection with forming iron oxide (Fe ₂ O ₃ ) by roasting an aqueous solution of iron chloride (FeCl ₂ ), the reaction is stable without undecomposed residual iron chloride. Industrially, the roasting treatment of spent acid in steel and the number of times of Fe ₂ O ₃ as a by-product have been extensively supported, which supports the results of equilibrium theory tests.

Fe ₂ O ₃ is very stable in HCl atmosphere and chlorination hardly occurs. Even when a mixture of Fe ₂ Cl ₃ and another metal (eg, MnFe ₂ O ₄ , MgFe ₂ O ₄ , CuFe ₂ O ₄ ) is reacted in 1% HCl-N ₂ at a temperature below 350 ° C., the iron component Iron oxide is not chlorinated in the same way as when used alone, and other metals form divalent metal chlorides. This fact also indicates the stability of iron oxide (Fe ₂ O ₃ ) to hydrogen chloride gas. (Transactions of Japan Chemical Society, No. 11, (1977), 1728-36).

That is, in the formation reaction of the Fe-Mn-Zn tertiary metal oxide, it is possible to promote the oxidation reaction of manganese and zinc chloride and to prevent the reaction of manganese and zinc oxide with the coexisting hydrogen chloride in the reaction product and to prevent the formation of chloride again. This is very important in terms of equilibrium theory and actual response.

The fifth invention of the present invention, i.e., the spray dew point of the atomized droplets sprayed from the spray nozzle is set to 200 µm or less and immediately after atomization roasting, these spray droplets are acidified within 10 seconds by a refrigerant containing H ₂ O and / or O ₂ . The method of immediately cooling to a temperature range of 400 ° C. or less will also be described later with reference to FIGS. 8 and 9. 8 is a correlation diagram showing the relationship between the time from atomization roast to cooling and the ZnO deviation, ie the difference in Zn content between the liquid composition and the reaction product converted in terms of ZnO. As can be appreciated from the diagram, the longer the time from atomization roast to cooling, the greater the ZnO deviation.

The reason is assumed to be as follows. If the powder is kept at high temperature and left for a long time in chlorine and / or hydrogen chloride gas after roasting, the zinc portion of the resulting oxide powder is converted to chloride, increasing residual chloride or increasing ZnO variation.

Therefore, it is necessary to cool the reaction product below 400 ° C. after the reaction is completed to stop the reaction in a practical sense. This time is within 10 seconds.

One reason for the ZnO deviation is due to the high vapor pressure of zinc chloride, and one requirement to avoid deviations caused by this high vapor pressure is that ZnCl ₂ is not cooled when cooled using a cold vessel containing H ₂ O and / or O ₂ . It is cooled below 400 ℃ which does not convert well into steam.

When hydrogen chloride in the atmosphere changes to hydrochloric acid by dewing after cooling, it quickly converts the oxides to chlorides, increasing the residual chlorides. Therefore, a temperature higher than the acid dew point must be ensured.

9 shows the relationship between the mole fraction of H ₂ O and / or O ₂ in the refrigerant and the mole fraction of Zn oxide in total Zn in relation to the total gas amount. If the mole fraction of H ₂ O and / or O ₂ in the refrigerant is smaller with respect to the total gas amount, the oxidation of Zn does not proceed.

The higher the mole fraction of H ₂ O and / or O ₂ in the refrigerant in the total gas amount is, the more preferable, but more than 3% is practically no problem.

Table 1 shows the chloride concentrations by chemical analysis of powders collected by a specific on-line sampling device that limits oxidation and re-chlorination in the sampling process of powders upon roasting of Fe-Mn-Zn chloride aqueous solution.

Tables 1 and 9 demonstrate that residual chlorides, in particular zinc chloride, can be degraded by performing cooling by using a refrigerant containing HO and / or O immediately after roasting, rather than simply by cooling or heat exchange with N or the like. .

In Table 1, the reason why Mn chloride does not change immediately after quenching is because the temperature at the time of cooling is too low, and it is estimated that the reaction does not proceed sufficiently even when the required amount of HO and / or O necessary for the reaction is present.

If the particulate diameter exceeds 200 m, the incidence of the resulting agglomerate particles of oxides increases, and the ZnO deviation increases for the reasons shown in FIG. 8 because the residence time in the reaction zone varies with the particle size.

Therefore, in order to promote the oxidation reaction of the chloride and to prevent the resulting oxide from reacting with the hydrogen chloride coexisting in the reaction system to change back to the chloride and to prevent sublimation thereof, the diameter of the atomized droplets is 200 μm or less, and HO and / or O It is necessary to perform cooling immediately after the atomization roasting at 400 ° C. or lower using a refrigerant containing, in which the cooling process is completed within 60 seconds, preferably within 10 seconds, so that the recovered powder is higher than the acid dew point. It is necessary to maintain at temperature, these are the prerequisites for limiting ZnO deviation.

10 is a schematic explanatory diagram of an apparatus for practicing the present invention. Symbol 1 represents an atomization roasting furnace. A vertically extending cylindrical roasting furnace, reinforced with refractory material, is used as the atomizing roasting furnace 1, and the cooler 4 is disposed near the roasting furnace 1. The lower part of the cooler 4 is connected to the lower part of the atomization roasting path through the passage 3, and the cooler nozzle 2 which can be quenched immediately after the atomization roasting is disposed in the circumferential direction of the cooler 4 at the end of the cooler 4.

On the other hand, the raw material spray nozzle 5 for spraying the chloride mixed solution as a starting material is arranged in the circumferential direction in such a manner as to surround the center burner 6 at the top of the atomization roasting furnace. Since the center burner burner 6 and the raw material spray nozzle 5 are disposed at adjacent positions in this manner, the aqueous solution from the raw material spray nozzle is not sprayed directly to the central burner. For this reason, the combustion flame is not cooled, and the raw material mixed solution is mixed with the gas after completion of combustion from around the central burner.

Thus, a high speed gas flow can be achieved which improves the mixing, and the mixed solution of starting chlorides is sprayed into the hot high temperature gas inside from the spray nozzle 5 to the roasting. In this case, the particulate maximum particle size is 200 μm or less, preferably 5 to 150 μm. Particulate particle size is a value at room temperature. This rapidly sprayed mixed solution is mixed with a high temperature vortex gas stream to be collectively maintained at a predetermined reaction temperature by latent heat of vaporization and heat of decomposition to proceed decomposition of the metal salt. In this case, reaction temperature is 600-1,000 degreeC, Preferably it is 750-900 degreeC. If the temperature is less than 600 DEG C, crystallization to the spinel structure for obtaining ferrite hardly proceeds, and the residence time has to be extended. If the residence time is extended, the zinc spinel is again chlorinated, increasing the zinc deviation. Conversely, if the temperature exceeds 1,000 ° C., when the starting material contains volatiles, the vaporization is faster, and the appropriate cooling time of the reaction product, generated by decomposition in the gas phase by the refrigerant containing HO and / or O, is achieved. Shorter than 60 seconds, problems arise.

As described above, the residence time is preferably as short as possible, preferably 10 seconds or less and preferably 0.1 to 5 seconds. The resulting mixture of particulates and hot gas after decomposition of the heavy metal salts in the roasting furnace is cooled by water sprayed from the chiller nozzle 2 disposed at the distal end of the chiller 4 in the circumferential direction as in the roasting furnace. The fine particles obtained are separated from the gas and collected by a cyclone or an electrostatic precipitator (not shown). In this case, the adsorbed hydrogen chloride is converted to hydrochloric acid due to dewing after cooling, and the oxide is quickly chlorinated to chloride. To avoid this problem, the internal temperature of cooler 4 is maintained above the acid dew point, and hydrogen chloride is recovered and used as the recovered acid in a conventional manner.

In addition, a second invention according to the present invention relates to an atomization roasting method that can obtain a soft ferrite raw material powder having an extremely low residual chloride content, and this method, within the predetermined range of the amount of HO and / or O in the atomization roasting Sufficiently performing the oxidation function by holding and performing quench immediately after roasting. In other words, if the HO mole fraction is less than 2% of the reaction, the oxygen necessary for the oxidation of metal chlorides, especially manganese chloride, is not secured, and the residual chlorine content in the powder after atomization roasting dramatically increases. If the HO mole fraction is at least 5% and the O mole fraction is at least 2%, the oxidation reaction of the metal chloride is sufficiently carried out so that the residual chlorine content is present to the extent that practically no problem arises.

The reason for this is as follows.

The decomposition oxidation reaction proceeds easily with iron chloride as described above. Even in the case of zinc chloride, quenching with refrigerants containing HO and / or O promotes oxidation and / or prevents re-chlorination reactions.

However, in the case of manganese chloride, if the amount of HO and / or O necessary for oxidation is sufficient, the oxidation level is first measured under high temperature conditions in the initial atomization step, and the change in oxidation level is determined by the amount of HO and / or O thereafter. It is small no matter how you change it. The results after quenching shown in Table 1 are presumed to be due to the residue of undecomposed manganese salt due to insufficient HO and / or O concentration in roasting reaction.

12 shows the burner structure to the atomization roasting furnace according to the present invention. That is, Figure 12 is a cross-sectional view of the atomization furnace for producing a ferrite composite oxide powder according to the present invention. The central burner 6 is disposed at the top of the furnace 1 of the atomization roast, and three or more liquid spray nozzles 5 are disposed in the circumferential direction of the central burner 6. The angle of its extended slope portion at the top of the vertical atomization roaster 1 and the roaster satisfies θ ≦ 50 °. When the angle θ exceeds 50 °, the roasting increases the length in the vertical direction of the top and increases the approach distance of the combustion air vortex flow emitted from the center burner, so that the effect of the swirling flow is near the lower part of the nozzle hole to the roaster. Will remain. As a result, once the atomized droplets are gathered at the center by roasting, the density of the droplets increases at the center by roasting. Increasing the direct hit of the droplets increases the inertia of the droplets and promotes the collision of the droplets on the wall with roasting, causing them to attach to the wall with roasting. For this reason, the normal expansion slope portion 7 by roasting is set at 50 degrees or less.

Next, the effect of this invention is demonstrated in detail with reference to an Example.

Example 1

Ferrite calcined powder having an average particle size of 400 kPa and having a composition of 71 wt% FeO71, 22 wt% MnO, 7 wt% ZnO, 200 ppm SiO, and 800 ppm CaO was obtained by atomization roasting. After granulation, the granules were formed into annular bodies having an outer diameter of 29 mm, an inner diameter of 18 mm and a height of 7 mm by adding 1.0% PVA as a binder. The molded article obtained was sintered for four periods under the sintering conditions set forth in claim 4. As a result, about 4.8 g / cm A dense sintered compact having a sintered density of was obtained. Table 2 shows the crystal grain sizes of the obtained sintered cores and their power loss at 100 ° C. and 1 MHz-50 mT. In Table 2, the average crystal size was measured by polishing the sintered compact and imaging the polished surface by an optical microscope. Invention No. For 1 to 3, it can be seen that the average crystal size is 2μm or less. Comparative Examples 1 and 2 shown in the table show the results of the sintered cores obtained by setting the sintering temperatures to 1,200 and 1,300 ° C, respectively. It will be clear from Table 2 that the sintered core of the present invention has extremely good power loss at high frequencies.

Example 2

FeO: MnO: ZnO = 68.4.: 27.8: 3.8 (Weight%) when FeCl, MnCl and ZnCl obtained by concentrating FeCl having a concentration of 24% to 40% by a heat recovery column were calculated for an oxide as a raw material mixed solution The aqueous solution containing the ratio of) was prepared, and sprayed as a solution having a maximum drop diameter of 50 to 150 μm at room temperature using spray air in the roaster shown in FIG. 10. The roasting temperature was set to 800 ° C. and the quenching time to 400 ° C. or lower was set to 2 seconds and 10 seconds in the examples of the present invention, and 60 seconds and 4 hours in the comparative example. The results are shown in FIG. In the comparative example where the quenching time was 60 seconds and 4 hours, the deviation of zinc was greatly increased as compared with the method of the present invention, and in particular, in the comparative example with the interval of 4 hours before cooling, almost no zinc was present in the powder. .

Analysis of the composition of the composite oxide obtained from the electroprecipitation apparatus (EP) after cooling revealed that the composition was FeO: MnO: ZnO = 68.1: 27.4: 4.2 (wt%).

Example 3

FeO: MnO: ZnO = 68.4: 27.8: 3.8 (wt%) when FeCl, MnCl and ZnCl obtained by concentrating FeCl having a concentration of 24% to 40% by a heat recovery column were calculated for an oxide as a raw material mixed solution. An aqueous solution containing a ratio of was prepared and sprayed as a solution having a maximum Paul diameter of 50 to 150 μm at room temperature using spray air in the roaster shown in FIG. The roasting temperature was set to 800 ° C. and the quenching time to 400 ° C. or lower was set to 5 seconds in the examples of the present invention. In two cases, the experiment was performed by dividing the HO mole fraction into 2%, 5%, 10% and 15% under the condition that the O mole fraction was kept at 7% under the condition that the HO mole fraction was kept at 10%. It was.

The results are shown in FIG. This figure shows the results obtained by varying the concentrations (fractions) of HO and O in the roasting furnace, collecting the powder thus prepared after the reaction by the above-described sampling method, and then performing chemical analysis. The amount of residual chlorine was a level which does not cause a problem substantially when the concentration of O is 2% or more and HO is 5% or more.

Example 4

FIG. 13 is a view of the roasting furnace obtained by varying the angle θ of the extended slope portion of the top part of the vertical atomization roasting furnace shown in FIG. 12 from 10 ° to 70 ° and arranging three liquid spray nozzles in the circumferential direction of the center burner. My atomization results are shown. In FIG. 13, the average droplet diameter was measured according to a particle coating slide method in which a glass plate coated with magnesium oxide powder was placed underneath, and traces of droplets remaining on the glass plate were enlarged by SEM and photographed. As shown in FIG. 13, when θ exceeds 50 °, the average droplet diameter seemed to increase. Next, when the thermal atomization test was performed using the angles θ 30 ° and 65 ° of the expansion slope of the top of the atomization roaster, respectively, the deposition amount of the powder on the wall surface of the roasting furnace was 1 at θ = 65 ° when θ was 30 °. / 2, and even when the powder is a fine powder of three-way soft ferrite with high binding force, no deposition of powder on the inner wall and the nozzle occurred by roasting, and fluctuations in the gas flow inside the nozzle by clogging or roasting. Did. In conclusion, the operation could be performed extremely stable. The drying time could also be greatly reduced, and the roasting and yield to obtain ferrite could also be improved.

As the test conditions, an aqueous solution containing FeCl, MnCl and ZnCl at concentrations of 300 g / l, 80 g / l and 40 g / l as the raw material mixed solution and atomization air (pressure (5 kg / cm 2 G) of the solution) The droplets were blown into a vertical roaster at a high speed of 30 m / sec and the reaction was carried out at an roasting temperature of 800 ° C.

Example 5

A ferrite raw material powder containing FeCl71, 22% by weight of MnO, 7% by weight of ZnO, 150ppm of SiO and 600ppm of CaO and having an average input of 400 kPa (primary particle size by SEM observation) was used as a raw material powder. After direct granulation and molding, the roasting atmosphere was controlled in a conventional manner while the powder was sintered at 1,100 ° C. to 1,350 ° C., thereby obtaining a sintered body having no irregular grain growth and having a grain size of 2 μm or more. If it is necessary to improve the formability for mass production as used in the conventional soft ferrite manufacturing step, the powder is first heat-treated at 200 to 900 ℃ to grow the particles to the primary particle size 0.3 to 1.0μm, Grinding was performed to control cohesion which had a significant effect on sinterability. In this way, soft ferrite raw materials having various average secondary particle diameters (micro-track particle diameter: D) could be obtained. 14 shows a soft ferrite core using the soft ferrite raw material powder of the present invention having a primary particle size of 0.3 to 0.7 μm and a soft ferrite obtained by sintering a conventional soft ferrite raw material powder using iron oxide, manganese oxide and zinc oxide as raw materials. Power loss and saturation flux density of the core. Core sintering temperature was 1,300 degreeC. The raw material produced by the so-called build-up method using the fine powder of the present invention as a base showed high stability and high performance in a wide range of particle size distribution, and the material of the present invention had a saturation flux density shown in Fig. 14 (a). And in terms of power loss shown in Fig. 14 (b), they were superior to the conventional raw materials.

Example 6

When the soft ferrite raw material powder of the present invention is heat-treated at 400 ° C., the raw material powder which caused the grain growth as a starting material and the average secondary particle size are adjusted to around 1.1 μm, in particular, obtain high density and excellent characteristics which could not be obtained in the past. Could. The electromagnetic characteristics of the sintered compact are summarized in Table 3.

This sintered body is 5.00g / cm It had a sintered density of, almost no voids and abnormal grain growth, and uniform particle size. That is, cores having desirable characteristics comparable to those of the HIP sintered body could be produced by the normal pressure sintering method.

* μi: Initial permeability

** Power Loss: Value at 100KHz, 200mT, 100 ℃

As can be clearly understood from the examples given above, the calcined powders produced by conventional processes or the calcined powders obtained by the so-called break-down method are of various properties due to the generation of very fine powders resulting from excessive grinding. Problems such as heterogeneity of molded products due to deterioration and the presence of hard aggregates, micro heterogeneity in both powders and compositions causing abnormal grain growth of sintered crystals, but the use of the raw powder of the present invention One sintered body can be easily obtained. Another remarkable feature of the present invention is that when the soft ferrite raw material powder having a predetermined composition according to the present invention is used and the sintering conditions of the molded product thereof are adjusted, the crystal structure of the final sintered body can be arbitrarily adjusted. For example, according to the present invention, it is possible to easily produce a soft ferrite core having excellent power loss in the high frequency band, particularly the MHz band, and the present invention is greatly effective in reducing the size of the high frequency transformer.

In terms of the manufacturing process, the present invention is able to make extremely low component deviations of the recovered powder with respect to the liquid composition of the zinc-containing high vapor pressure material, and Zn concentration due to the quenching effect using the refrigerant containing HO and / or O. The soft ferrite raw material powder of 20 wt% or more can be easily produced. The present invention can reduce the amount of residual chlorides, reduce the coordination burden of components until the dechlorination step after roasting, and also shorten the production step.

In terms of soft ferrite raw powder, the quality grades of iron oxide, manganese oxide, and zinc oxide as starting materials have undergone past changes depending on the performance required for soft ferrite. For this reason, the characteristics of the powders have been determined and the method of producing soft ferrites, from treatment of starting materials to calcination conditions and granulation molding conditions, must be subtly changed according to the required quality of soft ferrites. Since the electric power production conditions of the soft ferrite raw material powder of the present invention can be applied to all soft ferrites in common, it is easy to operate the molding and sintering processes. In addition, since the primary component can be produced by a through-process, the control of the impurity content can also be easily performed according to the desired quality, which is an advantage in process. When the present invention is applied as described above, the present invention can simultaneously satisfy the drastic reduction and stabilization of production cost and higher performance. Thus, the present invention provides extremely significant practical effects.

Claims (11)

The composition ratio of Fe, Mn, and Zn is 65 to 85 wt% in terms of Fe ₂ O ₃ for Fe, 10 to 30 wt% in terms of MnO for Mn, and 2 in terms of ZnO for Zn. It is maintained at 25wt%, P and Cr as a trace component, satisfying P≤20ppm, Cr≤50ppm, the average particle diameter is characterized by a microscopically homogeneous composition variation of Fe ₂ O ₃ , MnO and ZnO 0.1μm Mn-Zn type soft ferrite raw material powder manufactured by the high temperature oxidation method below. The composition ratio of Fe, Mn, and Zn is 65 to 85 wt% in terms of Fe ₂ O ₃ for Fe, 10 to 30 wt% in terms of MnO for Mn, and 2 in terms of ZnO for Zn. It is maintained at 25wt%, P and Cr as a trace component satisfying P≤20ppm, Cr≤50 ppm, characterized in that the microscopically homogeneous composition variation of Fe ₂ O ₃ , MnO and ZnO, the average particle size A soft ferrite sintered body obtained by steady pressure sintering an Mn-Zn type soft ferrite raw material powder which is 0.1 m or less and produced by a high temperature oxidation method. The composition ratio of Fe, Mn, and Zn is 65 to 85% in terms of Fe ₂ O ₃ for Fe, 10 to 30% by weight in terms of MnO for Mn, and 2 in terms of ZnO for Zn. It is maintained at 25 to 25% by weight, P and Cr as a trace component satisfies P≤20ppm, Cr≤50ppm, characterized by the microscopically homogeneous compositional variation of Fe ₂ O ₃ MnO and ZnO, the average particle diameter is 0.1 A soft ferrite sintered body having an average crystal grain size of 2 μm or less, obtained by directly granulating and molding a Mn-Zn type soft ferrite raw material powder produced by a high temperature oxidation method of less than μm and sintering at a temperature of less than 1,100 ° C. The temperature rise up to 400 ° C. is carried out in the air to remove the binder, and the atmosphere of the subsequent temperature increase process is maintained in a nitrogen atmosphere having an oxygen content of 100 ppm or less, so that the density of the finally obtained sintered compact is 4.7 g / cm 3 or more. Characterized in that the composition ratio of Fe, Mn, and Zn is 65 to 85 wt% in terms of Fe ₂ O ₃ for Fe, 10 to 30 wt% in terms of MnO for Mn, ZnO for Zn It is maintained at 2 to 25wt% in terms of conversion, P and Cr as a trace component satisfies P≤20ppm, Cr≤50ppm, and the composition deviation of Fe ₂ O ₃ , MnO and ZnO is microscopically homogeneous, and the average particle diameter The soft ferrite element having an average crystal grain size of not more than 0.1 μm and obtained by direct granulation of the Mn-Zn type soft ferrite raw material powder produced by the high temperature oxidation method, followed by sintering under normal pressure at a temperature of less than 1,100 ° C. Manufacturing method of ferrite sintered body during sintering process The diameter of the atomized droplets sprayed from the spray nozzle is kept below 200 μm, and cooled immediately after the atomization roast and 10 seconds by using a refrigerant containing H ₂ O and / or O ₂ at an acid dew point above 400 ° C. or less. A method for producing a soft ferrite raw powder by atomization roasting method by mixing Fe, Mn and Zn in the form of chloride, characterized in that to carry out. The soft ferrite raw material according to claim 5, wherein the trivalent Fe ions contained in the chloride solution constituting the ferrite to be supplied to the atomization roasting step through the concentration step are reduced to divalent Fe ions to limit the amount of trivalent Fe ions. Method for preparing the powder. The soft ferrite according to claim 5, wherein one or both of the metal Mn and the metal Zn are added to the starting chloride supplied to the roasting step through a concentration step to reduce trivalent Fe ions in the starting chloride to divalent Fe ions. Manufacturing method of raw powder. By adding Mn and Zn as ferrite elements other than Fe, trivalent Fe ions contained in the raw chloride solution fed to the atomization roasting step through the concentration step are reduced to divalent Fe ions, while hydrochloric acid in an amount exceeding equilibrium Maintain; Mn and Zn are further added as necessary as ferrite elements other than Fe to reduce the free acid present; adjust pH to 1-4; An oxygen gas such as air is charged to the solution to form Fe oxide; After filling with a further prepared Fe oxide, such as goethite; Removal of impurities by adsorption; A method for preparing a chloride solution containing Fe, Mn and Zn, comprising the step of limiting P and Cr impurities. While maintaining the reaction temperature below 600 ℃ H ₂ O mole fraction and O ₂ mole fraction is maintained at more than 5% and 2% or more, respectively, and then quenched within 10 seconds at the temperature above the acid dew point, below 400 ℃ A method for producing a soft ferrite raw material powder when the soft ferrite raw material powder is produced by atomization roasting method by mixing Fe, Mn and Zn in the form of chloride. The center burner is located at the top of the main body by roasting, and three or more liquid crystal spray nozzles capable of spraying liquid crystals having a particle diameter of 200 μm or less are arranged in the circumferential direction of the center burner, and the roasting angle θ of the extended slope portion of the top is Less granulated roasting powder for obtaining ferrite raw powder by using metal chloride as starting material, characterized by being set at 0 ° ≦ θ ≦ 50 ° C. to reduce the collection of liquid crystals to be sprayed. 12. The atomization roast nozzle according to claim 10, wherein the distal end of the atomizing roast nozzle of the two liquids to be atomized and roasted is made streamlined, and a gas outlet passage is disposed around the outer circumferential portion of the distal end of the atomizing roast nozzle at the end of the atomizing roast nozzle. The less adherent atomization roast of powder characterized by canceling the eddy current and preventing the adsorption of solid substance generated from the solution.