JP6585540B2 - Iron oxide for MnZn-based ferrite raw material, MnZn-based ferrite and method for producing MnZn-based ferrite - Google Patents

Description

  The present invention relates to iron oxide for MnZn-based ferrite raw materials, MnZn-based ferrite using the same, and a method for producing MnZn-based ferrite.

  MnZn-based ferrite is used in electronic components such as switching power supplies, noise filters, and choke coils. In recent years, since the performance of these electronic components has been improved, improvement in the magnetic properties of MnZn-based ferrite has been demanded with the improvement in performance.

In particular, a ferrite core used for a transformer of a switching power supply may have a core loss of 300 kW / m ³ or less at a frequency of 100 kHz, a magnetic flux density of 200 mT, and a temperature of 100 ° C. even in a relatively inexpensive general-purpose product. There is an increasing demand for products that are equivalent to high-performance products.

  Also, this ferrite core is usually manufactured in a mass production of tens of thousands at a time. And even if it is such a big production unit, it is calculated | required that the whole quantity satisfies a specification value.

  Therefore, it is extremely important to reduce the variation in the core loss from lot to lot as well as the average value of the core loss is low in all manufactured cores. Furthermore, as a manufacturing method, it is desired to have a simpler process and to be manufactured at a low cost.

  Here, the manufacture of the ferrite core is performed by mixing the Mn source and the Zn source into the raw iron oxide, then calcining, pulverizing, and granulating as necessary, and then into a predetermined shape. It is common to go through a step of molding and charging the molded body into a firing furnace.

And when the dispersion | variation in the characteristic is easy to receive to the influence of a manufacturing process like MnZn type ferrite, the uniformity of the raw material mixing in the first process of a manufacturing process becomes important especially.
Therefore, in the conventional MnZn-based ferrite raw material mixing step, wet mixing using water is performed using a ball mill, an attrition mill or the like so that each raw material powder is uniformly mixed (patent) Reference 1).

Here, from the viewpoint of simplicity of the manufacturing process, productivity, or cost, there is a great advantage in dry mixing using a vibration mill or the like.
However, since the characteristic variation of the final core is larger than that of wet mixing, wet mixing has been adopted as described above when manufacturing MnZn-based ferrite and the like.

  In this regard, Patent Document 2 proposes a technique for evenly obtaining particularly high initial magnetic permeability even when the mixing of iron oxide or the like of the MnZn-based ferrite raw material is performed by a dry method.

JP-A-11-144934 JP 2003-073124 A

  The technique described in Patent Document 2 makes it possible to obtain a high initial permeability even when the MnZn-based ferrite raw material such as iron oxide is mixed in a dry manner. On the other hand, as described above, even in general-purpose products, core loss is particularly required to be stable and low. It is desired to realize this core loss characteristic even when the mixing of MnZn-based ferrite raw material such as iron oxide is performed by a dry method.

  The present invention has been made in view of the above circumstances, and is a transformer for a switching power supply that uniformly exhibits low core loss characteristics even when the MnZn-based ferrite raw material such as iron oxide is mixed in a dry manner. MnZn-based ferrite suitable for use and iron oxide for raw material of the MnZn-based ferrite are provided, and even if dry mixing is advantageous in terms of simplicity of production process, productivity and cost, low core loss It aims at establishing the manufacturing method of the MnZn type ferrite using this iron oxide expressed uniformly.

The inventors have a simple manufacturing process using dry mixing that can be manufactured at low cost, and the core loss is low such that the frequency is 100 kHz, the magnetic flux density is 200 mT, the temperature is 100 ° C., and is 300 kW / m ³ or less. In the production of MnZn-based ferrite with core loss, we intensively studied what kind of raw material iron oxide can be used to reduce the variation of core loss in the final core.

  In particular, the inventors specify the types of impurities in the raw iron oxide that cause the core loss of the low-loss MnZn-based ferrite and the limit amount thereof, that is, a typical method for producing conventional raw iron oxide. Instead of reducing all impurities uniformly as in the crystal refining method, conversely, studies were made on the increase and decrease of impurities, including addition if necessary.

  As a result, it has been newly found that a high Mn content that is not within the standard of ferrous oxide for ferrite defined in JIS K1462 is suitable as a raw material for obtaining ferrite with an equally low core loss. That is, using iron oxide with a high content of Mn, which has not been used at all, as a raw material, the amount of Mn and the amount of Cl in the iron oxide with a high content of Mn are regulated to predetermined amounts, and further, B ( By suppressing the amount of boron) within a certain range, it has been found that even in a process using dry mixing, a MnZn-based ferrite that uniformly expresses a low core loss can be obtained, and the present invention has been completed. It was.

That is, the gist configuration of the present invention is as follows.
1. Mn: 0.30 mass percent 2.5 wt% or less and Cl: Cl ^- as a MnZn ferrite material for iron oxide containing 0.10 to 0.20 mass%, the mixed amount of B 3. An iron oxide for a MnZn-based ferrite raw material characterized by being suppressed to 0 mass ppm or less.

2. The MnZn-based ferrite using the iron oxide for the MnZn-based ferrite material as described in 1 above as a raw material,
MnO: 33.0-40.0 mol%
ZnO: 6.0 to 14.0 mol%
MnZn-based ferrite, the balance of which consists of Fe ₂ O ₃ and inevitable impurities.

3. A MnZn-based ferrite composed of a basic component, subcomponents and inevitable impurities,
MnO: 33.0-40.0 mol%
ZnO: 6.0 to 14.0 mol%
Fe ₂ O ₃ : In the basic component consisting of the balance, Cl: 0.08 to 0.13% by mass as the accessory component
And the amount of B in the inevitable impurities is
B: MnZn system ferrite which is 3 mass ppm or less.

4). The MnZn ferrite is
Furthermore, the MnZn ferrite according to 2 or 3, further comprising at least one selected from calcium oxide, silicon dioxide, bismuth oxide, indium oxide, vanadium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide and molybdenum oxide. .

5. A method for producing MnZn-based ferrite, comprising dry-mixing the iron oxide for ferrite raw material described in 1 above, a Mn source and a Zn source, followed by calcining, molding, and firing.

Using the iron oxide for raw materials of the present invention, even when mixing raw materials not by wet mixing that is inferior in cost and productivity but by dry mixing that is simple and complete in a short time, low core loss is uniformly expressed It can be used as a mixed raw material for MnZn-based ferrite.
Further, according to the present invention, it is possible to establish a method for producing MnZn-based ferrite that uniformly expresses a low core loss by using dry mixing which is advantageous in terms of simplicity of production process, productivity and cost. Therefore, this manufacturing method can provide an inexpensive MnZn-based ferrite that uniformly expresses a low core loss.

Hereinafter, the elucidation process of the present invention will be described.
In general, iron oxide used as a ferrite raw material is iron oxide produced as a by-product when hydrochloric acid is recovered from a effluent obtained by hydrochloric acid pickling the surface of a thin steel plate.
For this reason, since a large amount of impurities in the steel sheet, industrial water, and the like are mixed, various techniques have been proposed in order to remove the impurities and make a composition that can be used as a ferrite raw material.

  As the above technique, first, there is a crystal purification method. This crystal purification method is performed by, for example, iron sulfate or chloride from an aqueous solution of iron sulfate or iron chloride as described in JP-A-7-176420. Iron crystals are crystallized, and the crystals are oxidized to iron oxide.

  However, in this method, since a part of the impurities is mixed in the crystal, removal of the impurities is not always sufficient in one crystallization. For this reason, it is necessary to repeat the treatment such as dissolving the crystallized crystal in water containing no impurities and recrystallizing it.

  In addition, since this method uses segregation during crystal crystallization, the degree of segregation varies depending on the type of impurities. Especially when trying to reduce impurities with a small degree of segregation, the method is repeated many times. It is necessary to repeat dissolution and recrystallization.

  Furthermore, this method has the advantage that all kinds of impurities can be reduced as much as necessary in principle by increasing the number of times of re-dissolution / recrystallization, but of course the cost becomes enormous. End up.

  Therefore, in reality, re-dissolution / recrystallization is terminated at an appropriate number of times with some impurities remaining, but the disadvantage of complicated manufacturing process and high cost is not completely solved.

Here, the impurities of iron oxide include a harmful impurity and an impurity that is not so as to develop various ferrite characteristics. However, in the crystal refining method described above, optimizing the impurity content for each type of ferrite becomes extremely complicated and causes an increase in cost.
Therefore, as a general-purpose iron oxide for ferrite, iron oxide in which the amounts of various impurities defined in JIS K1462 are uniformly reduced has been used.

  However, for example, in the case of the above-described use of ferrite, as described above, it is not always necessary to reduce all kinds of impurities.

  In particular, in the present invention, it is not necessary to suppress Mn as an impurity contained in iron oxide to 0.30% by mass or less as defined in JIS K1462, but rather to exceed 0.30% by mass, the amount of Cl And controlling the amount of B together have necessary and sufficient conditions as a raw material for MnZn-based ferrite that uniformly expresses low core loss.

That is, the iron oxide for MnZn-based ferrite raw materials according to the present invention is an iron oxide that has been used outside the standard of JIS K1462 and has not been used, that is, the Mn content is more than 0.30% by mass and more than 2.5%. And a composition in which the Cl content is in the range of 0.10 to 0.20 mass% with Cl ⁻ ions and the B content is suppressed to 3.0 mass ppm or less. It is what you have.

The iron oxide having this composition can be produced by a relatively simple roasting method such as spray roasting or fluid roasting of an iron chloride aqueous solution, as will be described later.
Therefore, in the present invention, it is manufactured by spray roasting or fluid roasting of an aqueous solution of iron chloride that can be mass-produced at a relatively low cost rather than iron oxide manufactured at high cost as in the crystal refining method. It is possible to target iron oxide that has been excluded as a product.

Here, Mn and Cl contained in iron oxide are oxidized by evaporation of water when Mn and Cl ^- ions dissolved in the hydrochloric acid pickling effluent of the steel plate are collected by spray roasting or fluid roasting. It has been moved to iron.

  First of all, the existence form of Mn in iron oxide has not been analyzed because its content is small, but the iron oxide particles have a shape like manganese ferrite with the same spinel structure as MnZn ferrite. It is presumed that it is incorporated in the crystal lattice.

  Therefore, since it is insoluble in water, it is difficult to remove even in the final water washing step of the iron oxide production process. As described in this publication, Mn is included in the range of 0.10 to 0.30 mass%.

However, in order to reduce the core loss evenly, it is necessary to increase the amount of MnO in ferrite, and similarly, it is necessary to increase the amount of Mn in iron oxide.
By the way, in recent years, in the iron and steel industry, steel sheets with higher strength and higher function than automobile steel sheets have been produced in large quantities. In order to realize such functions, steel sheets are compared with conventional steel sheets. The amount of Mn contained in is gradually increasing. For this reason, the amount of Mn contained in the hydrochloric acid pickling waste liquid of the steel sheet also increases, and the iron oxide after roasting causes the Mn amount to exceed 0.30% by mass, which is the JIS standard value of iron oxide for ferrite. Has also come to be seen often. It is possible to use iron oxide whose Mn content deviates from the standard value. Conventionally, such iron oxide has not been used as an iron oxide for ferrite and has been disposed of or used for other purposes such as pigments. Therefore, the Mn content of iron oxide can be increased by using iron oxide, which has been limited in the range of reuse.

On the other hand, since Cl ^- ions are soluble, the content can be adjusted by washing with water in the final step of the iron oxide production process, if necessary. Therefore, Cl ⁻ ions, which are important control parameters of the present invention, can be easily adjusted to a content ratio of 0.10 to 0.20 mass% with respect to iron oxide.

  Further, since B is insoluble in water like Mn, it is difficult to remove it even in the final water washing step of the iron oxide production process, so that B in the hydrochloric acid pickling waste liquid of the steel sheet remains as it is. Therefore, B can be adjusted by selecting a solution having a small amount of B in the hydrochloric acid pickling drainage of the steel sheet used for roasting. Moreover, when there is much B amount, it can reduce by means, such as adjusting an atmosphere by the calcination process of a raw material. However, since this method involves an increase in cost, it is fundamental to select a hydrochloric acid pickling solution with as little B amount as possible.

Here, when producing MnZn-based ferrite using iron oxide containing 0.1 to 0.3% by mass of Mn and 0.10 to 0.20% by mass of Cl ⁻ ions as a raw material, mixing of the raw materials is performed. In the case of wet processing, there are few technical problems, but there are problems in terms of cost.
Further, when iron oxide with Mn of 0.1 to 0.3% by mass and Cl ⁻ ion of 0.10 to 0.20% by mass using a dry mixing method is a raw material, the average value of MnZn-based ferrite core loss As described above, the problem is that even if the same degree as in the case of the wet method can be realized, the variation becomes large.

  On the other hand, as described above, when the raw material is dry-mixed using iron oxide having a Mn content of more than 0.30% by mass, which has hardly been used so far, the average value of the core loss of MnZn-based ferrite and Whether the average value of the core loss of the MnZn-based ferrite itself can be reduced is important.

As a result of various investigations on iron oxide raw materials having a high Mn content, the inventors specified the amount of Mn and the amount of Cl in iron oxide (in terms of Cl ^- ions), and further limited the B amount. Then, it has been found that not only the reduction of the average value of the core loss of the MnZn-based ferrite can be achieved but also the variation can be reduced.

Hereinafter, the composition of the iron oxide of the present invention will be described. The amount of Mn contained in the iron oxide, the mass% of the Cl amount (Cl ⁻ ), and the mass ppm of the B amount are mass ratios with respect to the entire iron oxide. Further, the balance of iron oxide in the present invention is iron and inevitable impurities, but even if inevitable impurities are contained in an amount of about 0.5% by mass, the present invention is not affected.

  Here, the amount of Mn contained in the iron oxide is set in the range of more than 0.30% by mass to 2.5% by mass or less when the raw materials are dry-mixed, which is 0.30% which has been excluded until now. This is because when the content exceeds 50%, both the average value of the core loss of the MnZn-based ferrite obtained when the raw materials are dry-mixed and variations in the average value can be reduced. On the other hand, when it exceeds 2.5 mass%, it becomes difficult to mix the Mn distribution uniformly depending on the dry mixing method, and the dispersion of core loss increases due to segregation of Mn. Note that it is preferable that the amount of Mn contained in the iron oxide is more than 0.31% by mass because variation can be further reduced.

Further, Cl is contained mainly in the form of FeCl _{2 in} iron oxide.
And was the range of 0.10 to 0.20 wt% as the amount of ions, the MnZn ferrite, Cl ^{- -} a Cl content in the iron oxide Cl the ion amount exceeds 0.20 mass%, This is because a desired low core loss value cannot be obtained. On the other hand, if it is less than 0.10% by mass, the core loss value and its variation become large, which causes an increase in cost during mass production. Note that the lower limit of the Cl 2 ⁻ ion amount is preferably more than 0.12% by mass in order to promote the homogenization reaction in calcination.

The reason why the Cl ⁻ ion may be in the range of 0.10 to 0.20 mass% when reducing the core loss in the ferrite has not yet been completely clarified, but when the Cl ⁻ ion is in this range, Cl during dry mixing ^- does not dissolve in water slurry as in the case of the wet method, will be present in the raw material until calcination. Therefore, it is considered that the calcining reaction between the basic raw material and the additive becomes more uniform and contributes to the reduction of core loss after the final firing.

  On the other hand, the amount of B mixed is suppressed to 3.0 mass ppm or less in order to make the crystal grain growth uniform and suppress the variation in core loss. If it exceeds 3.0 mass ppm, the number of crystals that grow abnormally increases, the specific resistance of the core decreases, the eddy current loss increases, and the core loss deteriorates. The lower limit of the amount of B mixed is not particularly limited. However, from the selection of hydrochloric acid pickling solution and analysis accuracy, the cost increases greatly when the amount of B is brought close to zero. preferable.

  Here, the amount of Mn contained in iron oxide can be controlled by adding to the waste hydrochloric acid solution to be used in the form of manganese chloride in addition to the amount originally contained in the waste acid.

  Further, the amount of Cl contained in iron oxide can also be controlled by adjusting the washing time in the final washing step or by adding it in the form of iron sulfate.

  Furthermore, the amount of B contained in the iron oxide may be adjusted by selecting a solution having a small amount of B from the hydrochloric acid pickling drainage solution of the steel sheet used for roasting.

Here, when the raw materials are dry-mixed, the cause of the influence of Mn and Cl in iron oxide and B on the variation of core loss in the final ferrite core has not yet been clarified. By containing in advance in the form of spinel of MnFe ₂ O _{4 in} iron oxide, and by limiting the amount of Cl ⁻ ions and B to the above-mentioned amounts, the reaction with the additive added and mixed later is possible. It is presumed that the uniformity of crystal growth is increased in the process from calcination to firing.

  In addition, about the influence of B among the trace components in the MnZn-based ferrite, for example, in Non-Patent Document 1, it is necessary to keep it to 50 ppm or less because the crystal structure is made non-uniform and the expression of high permeability is inhibited. Is described.

“Ferrite” (Hiraga et al., Maruzen, 1986), p. 92

However, regarding the reduction of the core loss, not the improvement of the magnetic permeability, when the iron oxide contains Mn and Cl ⁻ ions in the range according to the present invention, what is the specific amount of the influence of the B mixing amount starts from? There is no description in Non-Patent Document 1 mentioned above.
Therefore, when containing Mn and Cl ^- ions in the above-mentioned range, the variation of core loss in the final ferrite core can be reduced by further suppressing the amount of B mixed to 3.0 ppm or less. It can be said that it was found.

Next, the MnZn ferrite of the present invention will be described.
By using the iron oxide described above as a raw material and further dry-mixing a Mn source and a Zn source, which are usually used in the production of MnZn-based ferrite, after calcining, molding, and firing, An MnZn-based ferrite that uniformly expresses core loss can be obtained.

The basic component of MnZn-based ferrite in this invention, that is, the composition range of Fe ₂ O ₃ , MnO and ZnO is generally a core loss minimum value due to a small magnetic anisotropy and magnetostriction in the vicinity of 80 to 100 ° C. as a low loss material. From the viewpoint of how much the Curie point is set.

Normally, the composition of Fe ₂ O ₃ , MnO and ZnO is required because the magnetic anisotropy constant and magnetostriction constant are small and the core loss value is required to be low and minimal at an operating temperature in the range of about 80 to 100 ° C. The range is preferably as follows.
MnO: 33.0-40.0 mol%
ZnO: 6.0 to 14.0 mol%
Fe ₂ O ₃ : balance

That is, in the MnZn-based ferrite of the present invention, when MnO is less than 33.0 mol% or more than 40.0 mol%, or ZnO is less than 6.0 mol% or more than 14.0 mol%, the magnetic anisotropy constant and magnetostriction are reduced. The core loss is greatly reduced by the change of the constant and the change of the chemical composition of the spinel.
Preferably, MnO: 34.0~38.0mol%, ZnO: 8.0~13.0mol% and Fe ₂ O _3: a 52.0~54.0mol%, more preferably MnO: 34.5~ 37.5mol%, ZnO: 9.0~12.5mol% and Fe ₂ O _3: a 53.0~54.0mol%.

  As the MnO and ZnO raw materials, not only oxides but also compounds such as carbonates that can be changed to this form by firing can be used.

  Further, the MnZn-based ferrite of the present invention uses 0.06 to 0.13 mass%, preferably 0.10 to 0.03 mass% of Cl as a trace component (subcomponent) by using the iron oxide raw material described above. By containing 12% by mass and setting B in the inevitable impurities to 3.0 mass ppm or less, preferably less than 2.3 mass ppm, the core loss is low and the variation is reduced.

  The MnZn-based ferrite of the present invention has the above basic composition, but at least one of calcium oxide, silicon dioxide, bismuth oxide, indium oxide, vanadium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide and molybdenum oxide. Can be added.

As such MnZn-based ferrite,
Fe ₂ O ₃ —ZnO—MnO—CaOFe ₂ O ₃ —ZnO—MnO—SiO ₂ Fe ₂ O ₃ —ZnO—MnO—CaO—SiO ₂ Fe ₂ O ₃ —ZnO—MnO—CaO—SiO ₂ —TiO ₂ Fe ₂ O ₃ —ZnO—MnO—CaO—SiO ₂ —SnO ₂ Fe ₂ O ₃ —ZnO—MnO—CaO—SiO ₂ —Ta ₂ O ₅ —V ₂ O ₅ Fe ₂ O ₃ —ZnO—MnO—CaO—SiO _2- Nb ₂ O _{5 and the} like are exemplified, but the above examples are not limited to these examples as long as they satisfy the combination of bending at the grain boundary during sintering or forming a high resistance by solid solution in the grains. It is not limited.

In the above composition, CaO and SiO ₂ contribute to lowering the loss of MnZn-based ferrite by segregating at the grain boundaries, and V ₂ O _{5 as} a low melting point compound promotes crystal growth and contributes to higher magnetic permeability.

TiO ₂ and SnO ₂ contribute to lower loss by increasing the resistance inside the crystal, and Ta ₂ O ₅ and Nb ₂ O ₅ increasing the resistance of grain boundaries.

From the above viewpoint, the content of calcium oxide is 200 to 2000 mass ppm in terms of CaO, and the content of silicon dioxide is 50 to 400 mass ppm in terms of SiO ₂ . Further, the contents of vanadium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide, etc. are converted into V ₂ O ₅ , Ta ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , and SnO ₂ , respectively. It is preferably about 3000 mass ppm or less.

The contents of MnO, ZnO and Fe ₂ O ₃ which are basic components of the MnZn-based ferrite are expressed in mol% with respect to the total amount of MnO, ZnO and Fe ₂ O ₃ , and CaO, SiO ₂ , V ₂ O ₅ , the content of such _{ta 2 O 5, Nb 2 O} 5, TiO 2, SnO 2 shows a percentage of the total MnZn ferrite mass ppm.

  Further, the MnZn ferrite for the MnZn ferrite raw material of the present invention described above is dry-mixed with the Mn source and Zn source in the amounts described above, and then calcined, molded, and fired to produce MnZn ferrite. be able to. That is, the above-mentioned raw iron oxide is pulverized and mixed with a metal oxide such as Mn or Zn so as to finally have a desired composition of MnZn-based ferrite. This mixing is performed mechanically, and as described above, it is possible to perform a dry mixing here. At this time, metal oxides such as Ni, Mg, and Cu may be added up to about 500 ppm by mass.

  Next, the mixed oxide after pulverization and mixing is calcined by heating in a temperature range of 700 to 1100 ° C. in an atmosphere such as air, nitrogen, a mixed gas thereof, or a combustion exhaust gas of hydrocarbon fuel. . A rotary kiln or the like can be used for calcination.

The calcined mixed oxide is mixed with a trace amount of additive simultaneously with pulverization, and further fired after molding. At the time of mixing, a small amount of oxide powder such as CaO, SiO ₂ , V ₂ O ₅ , Ta ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ and SnO ₂ is added to improve the magnetic characteristics. The addition amount of these trace additives varies depending on the desired magnetic properties. A small amount of Zr, Cr, Co, Al and Mg oxides may be added as appropriate. The mixed pulverized powder thus obtained is usually adjusted to an average particle size of about 0.3 to 2 μm.

  The mixed pulverized powder is usually mixed with a molding aid represented by about 0.1 to 1% by mass of polyvinyl alcohol (PVA) and a lubricant represented by about 0.01 to 1% by mass of zinc stearate. Then, granulation is performed to a particle size of about −30 mesh to obtain a forming raw material.

  The molding raw material is molded into a desired shape by a pressure of about 10 to 200 MPa, for example. The molded body thus obtained is fired in the atmosphere, nitrogen, or a mixed gas thereof in a temperature range of about 1200 to 1350 ° C.

  Other steps for producing the iron oxide for MnZn-based ferrite and the MnZn-based ferrite are not particularly limited, and may follow a so-called ordinary method.

Hereinafter, the example which carried out the present invention concretely is explained.
In a batch-type melting tank filled with scraps (cold rolled steel plate scraps generated in steelworks) at a rate of more than 5 times the theoretical consumption, using as raw materials steel plate pickling waste solution containing hydrochloric acid mixed with various amounts of B The packing was stirred at a temperature of 90 ° C. for 2.5 hours to neutralize the free hydrochloric acid in the raw material and reduce the Fe ³⁺ to Fe ²⁺ to adjust the pH to 2.7. Next, after separating the liquid from the scrap material, air was dispersed in the liquid for 1.5 to 2 hours while maintaining the liquid temperature at 70 to 80 ° C. in the oxidation tank. Further, ammonia water was added to prevent pH reduction due to air oxidation or to control to an arbitrary pH value so that 2 to 4% by mass of Fe content in the solution was precipitated as a precipitate.
Subsequently, after adding the polymer flocculant with stirring, the polymer flocculant was left to settle and separate to obtain a clarified liquid. Finally, this clear aqueous iron chloride solution was roasted in a spray roasting furnace to obtain iron oxide.

In the series of processes described above, manganese chloride and iron sulfate were mixed in advance with the first steel sheet hydrochloric acid waste solution, and iron oxides containing various amounts of Mn, Cl ^- ions and B were obtained from the obtained iron oxide. Tables 1 and 2 show the amounts of Mn, Cl ^- ions and B in iron oxide. The balance in iron oxide was iron oxide and inevitable impurities.

Here, the amount of Mn and the amount of Cl 2 ⁻ ion in this example were measured with a fluorescent X-ray analyzer. The amount of B was measured with an ICP analyzer.

Next, using this iron oxide, an MnZn ferrite was produced. That is, the raw material oxides of each component were dry mixed for 10 minutes with a vibration mill and then calcined at 950 ° C. for 3 hours. Sub-components in the amounts shown in Tables 1 and 2 were added to this basic material, pulverized with a ball mill for 12 hours, and after firing by molding, a large number of rings having an outer diameter of 31 mm, an inner diameter of 19 mm, and a height of 8 mm A shaped compact was produced. Subsequently, these ring-shaped molded bodies were placed on a firing base plate (300 mm × 300 mm) side by side in 9 rows and 5 layers (total of 405 pieces) vertically and horizontally, and this base plate was placed in a continuous firing furnace. And calcining at a holding time of 1350 ° C. for 2 hours under the control of the oxygen concentration. Tables 1 and 2 show the amounts of MnO, ZnO, Fe ₂ O ₃ , SiO ₂ and CaO in the MnZn ferrite.
Furthermore, the amounts of Cl and B in these MnZn-based ferrites were analyzed again, and the results are also shown in Tables 1 and 2. The Cl content and B content were measured according to the ICP emission analysis method.

In order to evaluate the variation of the core loss of the MnZn-based ferrite core thus obtained, the average of the core loss Pcv (kW / m ³ ) at 100 kHz, 200 mT, and 100 ° C. for all 405 cores placed on each base plate. The value X and standard deviation S were measured. The coefficient of variation: S / X was defined as the degree of variation, and calculations were made for each of the examples.
The calculation results are also shown in Tables 1 and 2.

From the descriptions in Tables 1 and 2, the average value of core loss may be low regardless of the amount of Mn, the amount of Cl ^- ions and the amount of B in iron oxide, but in the inventive examples, the average value of core loss is further 250 kW / m ³ or less and the coefficient of variation is within 10%, indicating that it is an excellent low-loss material that has not only low core loss but also very little variation in core loss.

These results show that the Mn content in the iron oxide is 0.30% by mass or more and 2.5% by mass or less, the Cl content is 0.10 to 0.20% by mass as Cl ⁻ ions, and the B content is It can be seen that this can be realized by satisfying the range of 3.0 ppm by weight or less.

Claims (5)

Mn: 0.30 mass percent 2.5 wt% or less and Cl: Cl ^- as a MnZn ferrite material for iron oxide containing 0.10 to 0.20 mass%, the mixed amount of B 3. An iron oxide for a MnZn-based ferrite raw material characterized by being suppressed to 0 mass ppm or less. A MnZn-based ferrite using the iron oxide for MnZn-based ferrite raw material according to claim 1 as a raw material,
MnO: 33.0-40.0 mol%
ZnO: 6.0 to 14.0 mol%
MnZn-based ferrite, the balance of which consists of Fe ₂ O ₃ and inevitable impurities. Using the iron oxide for MnZn-based ferrite raw material according to claim 1 as a raw material,
A MnZn-based ferrite composed of a basic component, subcomponents and inevitable impurities,
MnO: 33.0-40.0 mol%
ZnO: 6.0 to 14.0 mol%
Fe ₂ O ₃ : In the basic component consisting of the balance, Cl: 0.08 to 0.13% by mass as the accessory component
And the amount of B in the inevitable impurities is
B: MnZn system ferrite which is 3 mass ppm or less. The MnZn ferrite is
The MnZn system according to claim 2 or 3, further comprising at least one selected from calcium oxide, silicon dioxide, bismuth oxide, indium oxide, vanadium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide and molybdenum oxide. Ferrite.   A method for producing MnZn-based ferrite, comprising dry-mixing the iron oxide for ferrite raw material according to claim 1 with a Mn source and a Zn source, followed by calcining, molding, and firing.