TWI761757B - Manganese-cobalt-zinc-based fertilizer granulated iron and method for producing the same - Google Patents

Abstract

The present invention provides a manganese-cobalt-zinc-based ferrite that has excellent magnetic properties and excellent mechanical properties and is preferably used for electronic parts for automobiles. In the manganese-cobalt-zinc-based fertilizer granulated iron of the present invention, the basic components and auxiliary components are adjusted to appropriate ranges, and the amounts of P, B, and Ti, which are unavoidable impurities, are respectively suppressed to P: less than 10 massppm and B: less than 10 massppm, Ti: less than 50 massppm, and the value of surface residual stress was made into less than 40 MPa.

Description

Manganese-cobalt-zinc-based fertilizer granulated iron and method for producing the same

The present invention relates to a manganese-cobalt-zinc (MnCoZn)-based ferrite that is particularly suitable for use in magnetic cores of automobile mounted parts, and a method for producing the same.

Manganese-zinc ferrite is a widely used material for noise filters such as switching power supplies, transformers, and magnetic cores for antennas. The characteristics of manganese-zinc ferrite include soft magnetic materials, which are high permeability and low loss in the kHz region, and are inexpensive compared to amorphous metals.

On the other hand, in the 10 MHz region, in the case of normal manganese-zinc ferrite, the specific resistance is low, and it is difficult to maintain the magnetic permeability due to attenuation due to eddy current loss. As a countermeasure, the following manganese-cobalt-zinc-based fertilizers are known, the content range of Fe ₂ O ₃ is selected to be less than 50 mol %, and Co ²⁺ ions which also exhibit positive magnetic anisotropy are used instead of the usual Cancellation of positive and negative magnetic anisotropy in manganese-zinc ferrite due to the presence of Fe ²⁺ ions with positive magnetic anisotropy. This manganese-cobalt-zinc-based ferrite is characterized by high specific resistance and good initial permeability up to the 10 MHz region.

However, as a magnetic core for an electronic device mounted on an automobile, the demand for which has been increasing due to the recent hybridization and electricalization of automobiles, it is required not to be damaged during use, that is, to have a particularly high fracture toughness value (Kic). This is because: the oxide magnetic materials headed by manganese-zinc ferrite are ceramics and brittle materials, so they are easily damaged, and Moreover, compared with the conventional home appliance application, the vehicle-mounted application is continuously used in an environment where it is constantly subjected to vibration and is easily damaged.

However, in automotive applications, weight reduction and space saving are also required. Therefore, in addition to having a high fracture toughness value, manganese-zinc ferrite and manganese-cobalt-zinc ferrite have the same preferable magnetic properties as those used in the past.

Various developments have been made in the past as manganese-zinc ferrite for use in automobiles.

Patent Document 1, Patent Document 2, etc. are reported as ferrous ferrite with good magnetic properties, and Patent Document 3, Patent Document 4, etc. are reported as manganese-zinc ferrite with improved fracture toughness value.

Furthermore, Patent Document 5, Patent Document 6, etc. are reported as high-resistance manganese-cobalt-zinc-based ferrous iron that maintains initial magnetic permeability even in the 10 MHz region.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-51052

[Patent Document 2] Japanese Patent Laid-Open No. 2012-76983

[Patent Document 3] Japanese Patent Laid-Open No. 4-318904

[Patent Document 4] Japanese Patent Laid-Open No. 4-177808

[Patent Document 5] Japanese Patent No. 4508626

[Patent Document 6] Japanese Patent No. 4554959

Generally, in order to increase the initial permeability of the conventional manganese-zinc ferrite, it is effective to reduce the magnetic anisotropy and magnetostriction. In order to realize these, it is necessary to set the blending amounts of Fe ₂ O ₃ , ZnO, and MnO, which are main components of manganese-zinc ferrite, in an appropriate range.

In addition, as a method of increasing the initial permeability of manganese-zinc ferrite in the high-frequency region, there are the following methods. That is, by applying sufficient heat in the calcination step, the crystal grains in the fertilized iron are appropriately grown, the movement of the magnetic walls in the crystal grains in the magnetization step is facilitated, and the component segregated at the grain boundary is added to generate Grain boundaries of moderate and uniform thickness. By this method, the specific resistance of the manganese-zinc ferrite is maintained, the attenuation of the initial permeability with the increase in frequency is suppressed, and a high initial permeability is realized even in the 100 kHz region.

However, in manganese-zinc fertilizer granulated iron, the highest specific resistance is only 20Ω. About m, it is impossible to maintain a high initial permeability to 10MHz under such specific resistance. Therefore, the above-mentioned manganese-cobalt-zinc-based ferrite is sometimes used in the 10 MHz region.

On the other hand, in addition to the above-mentioned magnetic properties, magnetic cores of electronic components for automobiles are required to have high fracture toughness values in order not to be damaged even in environments subjected to constant vibration. When the manganese-cobalt-zinc-based ferrite as the magnetic core is damaged, the inductance is greatly reduced, so the electronic components cannot achieve the desired function. And, because of its influence, the car as a whole is inoperable.

From the above, both the good magnetic properties represented by the high initial permeability and the high fracture toughness value are required for the magnetic core of the electronic components for automobiles. As a specific example, the required specific resistance is 30Ω. m or more, the initial permeability value at 23°C and 10MHz is 150 or more, the coercive force at 23°C is 15.0A/m or less, and the Curie temperature is 100°C or more. Excellent magnetic properties and flat samples Based on the Japanese Industrial Standards (Japanese Industrial Standards, JIS) R 1607 fracture toughness determination under the fracture toughness value of 1.00MPa. Excellent mechanical properties such as m ^1/2 or more.

However, in Patent Document 1 and Patent Document 2, although the composition for realizing the desired magnetic properties is mentioned, the fracture toughness value is not described at all. Similarly, in Patent Document 5 and Patent Document 6, the fracture toughness value is not mentioned, and it is considered that it is not suitable as a magnetic core of an in-vehicle electronic component.

In addition, in Patent Document 3 and Patent Document 4, although improvement of the fracture toughness value is mentioned, the magnetic properties are not sufficient as a magnetic core for automotive electronic components, and it is not suitable for the application.

Therefore, the present inventors first determined that among the basic components of manganese-cobalt-zinc-based ferrous iron, which can achieve high initial permeability at 23° C. and 10 MHz of a toroidal core, iron (in Fe ₂ O ₃ conversion) and cobalt (in CoO conversion) , and an appropriate amount of zinc (in terms of ZnO) were investigated.

As a result, the present inventors have found an appropriate range of the basic composition, in which the Fe ²⁺ ion, which is a cause of resistance reduction, is hardly contained, so that a certain high specific resistance can be maintained, In addition, since the magnetic anisotropy and magnetostriction are small, low coercivity, which is important as a soft magnetic material, a high Curie temperature that does not pose a practical problem, and a high initial permeability in the 10 MHz region can be maintained.

Next, the present inventors found that when SiO ₂ and CaO, which are non-magnetic components segregated at grain boundaries, are added in appropriate amounts, grain boundaries of uniform thickness can be formed in the manganese-cobalt-zinc-based ferrite, which results in an improvement in magnetic properties. In addition to the further increase in the effective specific resistance, the grain structure effective for improving the fracture toughness value can be adjusted.

Furthermore, the inventors of the present invention investigated factors that are effective in improving the fracture toughness value, and obtained the following two findings.

First, the present inventors discovered that it is necessary to suppress the growth of abnormal particles. The abnormal particle growth referred to in the present invention means that the balance of particle growth during calcination is disrupted due to the presence of impurities or the like, and some coarse particles (also referred to as abnormal particles in the present invention) with a size of about 100 normal particles appear. In addition, when the abnormal particle growth occurs, since the strength of this part is extremely low, the fat iron core is likely to be broken from this part as a starting point. Therefore, the suppression of abnormal particle growth in the ferrite is indispensable to the improvement of the fracture toughness value of the ferrite.

Next, the inventors of the present invention measured and examined the residual stress of the fertilized iron material based on X-ray diffraction on the surface of the fertilized iron. As a result, the present inventors found that there is a correlation between the value of residual stress and the value of fracture toughness. That is, a brittle material is a material that breaks due to tensile stress, but as long as the residual stress on the surface is a compressive stress or a tensile stress below a certain value, the propagation of cracks at the time of fracture can be suppressed, and the manganese-cobalt-zinc fertilizer granulated iron material The fracture toughness value increased.

From this viewpoint, the inventors conducted further investigations, and as a result, found a method for reducing the tensile stress remaining on the surface.

It is a method of immersing the calcined product after calcination in the process of manufacturing the ferrite core in an oxidizing liquid with a concentration of 10 N or more, such as nitric acid, sulfuric acid, or hydrochloric acid, for more than 0.50 hours. The surface of the conventional manganese-cobalt-zinc ferrite is in a slightly oxygen-deficient state due to the reduction reaction during calcination, and thus tensile stress is generated. However, using the above-mentioned oxygen When the chemical liquid is chemically oxidized, oxygen is given to the surface of the ferrite, which can reduce the tensile stress on the surface of the ferrite.

And in the manufacturing method of this invention, by using this method, the fracture toughness value of a material can be improved effectively.

Furthermore, Patent Document 7 and Patent Document 8 disclose the process of immersing the calcined iron ferrite in acid. However, in Patent Document 7, the acid concentration is as low as 1% to 5% (sulfuric acid corresponds to about 0.2N to 1.1N, nitric acid corresponds to about 0.2N to 0.8N, and hydrochloric acid corresponds to about 0.3N to 1.5N). In 8, the immersion time is as short as 6 minutes to 30 minutes, so the surface residual stress cannot be sufficiently reduced. In addition, in these documents, the purpose of impregnating iron ferrite is Cu dissolution and adjustment of the inductance L value, respectively, and there is no discussion of surface residual stress.

[Patent Document 7] Japanese Patent Laid-Open No. 2003-286072

[Patent Document 8] Japanese Patent Laid-Open No. 9-20554

In the aforementioned Patent Document 1 and Patent Document 2, the fracture toughness value is not mentioned, and it can be said that this improvement is impossible. Similarly, in Patent Document 5 and Patent Document 6, good magnetic properties with high initial permeability at 23° C. and 10 MHz are mentioned, but the fracture toughness value is not described.

In addition, in Patent Document 3 and Patent Document 4, although the toughness is improved, since an appropriate composition range cannot be selected, desired magnetic properties cannot be achieved.

Here, Patent Document 9 and Patent Document 10 describe that residual stress affects the flexural strength. However, the flexural strength in Patent Document 9 and Patent Document 10 is an important means for evaluating the strength of the outermost surface in particular, and in order to evaluate the strength of the outermost surface The bending strength when no pre-crack occurred was evaluated according to the strength of the site.

On the other hand, the improvement of fracture toughness which is the subject of this invention utilizes the process by predetermined acid. Therefore, it is necessary to evaluate the strength at a certain depth from the surface. Therefore, the fracture toughness value in this specification is evaluated by a bending test after a pre-crack is generated on the surface of the test piece.

In this way, in the manganese-cobalt-zinc-based fertilizer granulated iron in the present specification, the strength of a portion different from the above-mentioned Patent Document 9 and Patent Document 10 is important. method to evaluate. That is, about the said patent document 9 and patent document 10, and the manganese-cobalt-zinc-based fertilizer granulated iron in this specification, it can be seen that there is a large technical difference in the evaluation method of self-strength.

[Patent Document 9] Japanese Patent Laid-Open No. 2015-178442

[Patent Document 10] Japanese Patent Laid-Open No. 2015-178443

Therefore, the manganese-cobalt-zinc-based ferrite that is suitable for practically useful automotive parts, especially magnetic cores of automotive electronic parts, cannot be produced only by these known techniques.

The present invention has been made in order to solve the above-mentioned problems, and is based on the above-mentioned novel findings.

That is, the gist of the present invention is structured as follows.

1. a manganese-cobalt-zinc-based fertilizer granule iron, comprising basic components, auxiliary components and inevitable impurities, wherein as described basic components, comprising: iron: in terms of Fe ₂ O ₃ conversion is more than 45.0mol% and less than 50.0mol %, zinc: 15.5 mol % to 24.0 mol % in terms of ZnO, cobalt: 0.5 mol % to 4.0 mol % in terms of CoO, and manganese: the remainder, relative to the above-mentioned basic components, as auxiliary components, including: SiO ₂ : 50massppm to 300massppm and CaO: 300massppm to 1300massppm, the amounts of P, B, and Ti in the unavoidable impurities are respectively suppressed to, P: less than 10massppm, B: less than 10massppm, and Ti: less than 50massppm, The value of the surface residual stress of the manganese-cobalt-zinc-based ferric iron is less than 40 MPa.

2. The manganese-cobalt-zinc-based fertilizer granulated iron as described in 1, wherein the fracture toughness value of the manganese-cobalt-zinc-based fertilizer granulated iron based on the fracture toughness measurement of Japanese Industrial Standard R1607 is 1.00 MPa. m ^1/2 or more, and the initial permeability at 23°C and 10MHz is more than 150, and the specific resistance is 30Ω. m or more, the coercive force at 23°C is 15.0 A/m or less, and the Curie temperature is 100°C or more.

3. A method for producing manganese-cobalt-zinc-based fertilizer granulated iron, obtaining the manganese-cobalt-zinc-based fertilizer granulated iron as described in said 1 or said 2, comprising: a pre-calcination step, pre-calcining the mixture of the basic components, and cooling to obtain pre-calcined powder; in the mixing-pulverization step, auxiliary components are added to the pre-calcined powder obtained in the pre-calcination step, and Mixing and pulverizing to obtain pulverized powder; granulation step, adding a binder to the pulverized powder obtained in the mixing-pulverizing step and mixing, and then performing granulation; calcining step, in the granulation step obtained After the granulated powder is formed, it is calcined; and an impregnation step is immersed in acid, and the impregnation step immerses the calcined product obtained in the calcination step in an oxidizing liquid with a concentration of 10N or more for more than 0.50 hours.

4. The method for producing manganese-cobalt-zinc-based ferric iron according to item 3, wherein the oxidizing liquid is nitric acid, sulfuric acid, or hydrochloric acid.

The manganese-cobalt-zinc-based ferrite of the present invention has both excellent magnetic properties and excellent mechanical properties at a level that cannot be achieved by conventional manganese-cobalt-zinc ferrite, and is particularly suitable for use in magnetic cores of electronic parts for automobiles . As excellent magnetic properties, for example, the specific resistance is 30Ω. m or more, the value of the initial permeability at 23°C and 10 MHz is 150 or more, the coercive force at 23°C is 15.0 A/m or less, and the Curie temperature is 100°C or more. In addition, as excellent mechanical properties, for example, the fracture toughness value of the flat sample under the fracture toughness measurement based on JIS R 1607 is 1.00 MPa. m ^1/2 or more.

Hereinafter, the present invention will be specifically described.

First, the reason why the composition of manganese-cobalt-zinc-based ferric iron is limited to the above-mentioned range in the present invention will be explained. In addition, about iron, zinc, cobalt, and manganese contained in this invention as a basic component, all are represented by the value converted into _Fe2O3 , ZnO, _CoO , and MnO, respectively. In addition, the content of these Fe ₂ O ₃ , ZnO, CoO, and MnO is represented by mol %, and on the other hand, the content of auxiliary components and impurity components is represented by mass ppm (mass ppm) relative to the basic component.

Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%

When iron (Fe ₂ O ₃ ) is contained excessively, the amount of Fe ²⁺ increases, whereby the specific resistance of manganese-cobalt-zinc-based ferric iron decreases. In order to avoid this, it is necessary to suppress the amount of iron to be less than 50 mol % in terms of Fe ₂ O ₃ . On the other hand, when the amount of iron is too small, the coercive force of the fat iron will increase and the Curie temperature will decrease. In order to prevent this problem, the minimum content of iron is 45.0 mol % in terms of Fe ₂ O ₃ . The range of 47.1 mol% or more and less than 50.0 mol% is preferable. More preferably, it is in the range of 47.1 mol % to 49.5 mol %. The amount of Fe ₂ O ₃ is preferably 47.1 mol % or more, preferably less than 50.0 mol %, and more preferably 49.5 mol % or less.

ZnO: 15.5mol%~24.0mol%

Since zinc increases the saturation magnetization of ferrite and has a relatively low saturation vapor pressure, it has the effect of increasing the sintered density and is an effective component for reducing the coercivity. Therefore, it is assumed that zinc is contained in a minimum amount of 15.5 mol % in terms of ZnO. On the other hand, when the zinc content is more than a reasonable value, the Curie temperature is lowered, which is a practical problem. Therefore, the upper limit of zinc is 24.0 mol % in terms of ZnO. The preferable range of the amount of ZnO is 15.5 mol % to 23.0 mol %, and more preferably 17.0 mol % to 23.0 mol %. The amount of ZnO is preferably 17.0 mol % or more, more preferably 23.0 mol % or less.

CoO: 0.5mol%~4.0mol%

Co ²⁺ ions in cobalt (CoO) are ions having positive magnetic anisotropy energy, and with the addition of an appropriate amount of this CoO, the absolute value of the total magnetic anisotropy energy decreases, resulting in a decrease in coercivity. Therefore, it is necessary to add 0.5 mol% or more of CoO. On the other hand, the addition of a large amount of cobalt causes an increase in the coercive force due to a decrease in specific resistance, initiation of abnormal particle growth, and an excessively positive total magnetic anisotropy energy. In order to prevent this, the addition of CoO was limited to 4.0 mol % at most. The preferred range of CoO is 1.0 mol % to 3.0 mol %. The amount of CoO is preferably 1.0 mol % or more, and preferably 3.0 mol % or less.

MnO: the remainder

The present invention is manganese-cobalt-zinc-based fertilizer granulated iron, and the remainder of the main component composition is set to manganese (MnO). The reason for this is that, without manganese, it is difficult to obtain good magnetic properties represented by low coercivity and high permeability at 10 MHz. The preferred range of MnO is 25.0 mol% to 32.0 mol%. More preferably, it is 26.0 mol % - 33.0 mol %, More preferably, it is the range of 26.5 mol % - 32.0 mol %. The amount of MnO is preferably 25.0 mol % or more, more preferably 26.0 mol %, still more preferably 26.5 mol % or more, preferably 33.0 mol % or less, and more preferably 32.0 mol % or less.

The basic components have been described above, but the auxiliary components are as follows.

SiO ₂ : 50massppm~300massppm

It is known that SiO ₂ contributes to the homogenization of the ferrite crystal structure. Therefore, by adding an appropriate amount of SiO ₂ , the growth of abnormal particles can be suppressed, and the specific resistance can also be increased, so that the coercive force can be reduced, and the fracture toughness value can be improved at the same time. Therefore, a minimum of 50 massppm of SiO ₂ should be contained. On the other hand, when the addition amount of SiO ₂ is too large, abnormal particle growth occurs instead. While the fracture toughness value is significantly reduced, the initial permeability and coercivity at 10MHz are also significantly deteriorated. Therefore, the content of SiO ₂ needs to be limited to less than 300 massppm. The amount of SiO ₂ is preferably in the range of 60 massppm to 250 massppm, preferably 60 massppm or more, preferably 250 massppm or less, more preferably 190 massppm or less.

CaO: 300massppm~1300massppm

CaO has the effect of segregating at the grain boundary of manganese-cobalt-zinc ferrite and inhibiting grain growth. Therefore, with the addition of an appropriate amount of CaO, the specific resistance increases, the coercive force also decreases, and the fracture toughness value can also be increased. Therefore, it is made to contain CaO of 300 massppm at least. On the other hand, when the amount of CaO added is too large, abnormal particles will appear, and both the fracture toughness value and the coercive force will deteriorate. Therefore, the content of CaO needs to be limited to 1300 massppm or less. The preferable content of CaO is in the range of 350 massppm to 1200 massppm, more preferably in the range of 350 massppm to 1000 massppm. The amount of CaO is preferably 350 massppm or more, more preferably 500 massppm or more, preferably 1200 massppm or less, more preferably 1000 massppm or less.

Next, the unavoidable impurity components to be suppressed will be described.

P: Less than 10massppm, B: Less than 10massppm, Ti: Less than 50massppm

These are components which are unavoidably contained mainly in the raw material iron oxide. There is no problem as long as the contents of P and B are extremely small. However, when P and B are contained above a certain level, abnormal particle growth of ferrite iron occurs, and this part becomes the starting point of fracture, so the fracture toughness value decreases, and the coercive force increases and the initial permeability decreases. produce huge adverse effects. Therefore, the contents of both P and B were suppressed to less than 10 massppm. The preferable amounts of P and B are both 8 massppm or less. The content of P is preferably 8 massppm or less, and the content of B is preferably 8 massppm or less.

In addition, when the content of Ti is large, not only the fracture toughness but also the specific resistance, coercive force, and initial permeability of ferrite are deteriorated. Therefore, the content of Ti is controlled to be less than 50 massppm. The content of Ti is preferably less than 40 massppm, more preferably less than 30 massppm.

In addition, not limited to the composition, the properties of manganese-cobalt-zinc ferrite are greatly affected by various parameters. Therefore, in the present invention, in order to have better magnetic properties and strength properties, the following regulations may be further provided.

Fracture toughness value of fine ceramics based on JIS R 1607: 1.00MPa. m ^1/2 or more

Manganese-cobalt-zinc-based ferrite is a ceramic and a brittle material, so plastic deformation hardly occurs. Therefore, the single-edge precracked beam method (Single-Edge-Precracked-Beam method, SEPB method) prescribed|regulated by JIS R 1607 was used for the evaluation of fracture toughness. In this SEPB method, the fracture toughness value (Kic) is measured by forming a Vickers indentation at the center of the measurement object and performing a bending test in a state where a pre-crack is applied. The manganese-cobalt-zinc-based fertilizer granulated iron of the present invention is assumed to be used in automobiles requiring high toughness, and the fracture toughness value obtained by the SEPB method is ideally 1.00 MPa. m ^1/2 or more.

In order to satisfy the condition of the fracture toughness value, the value of the surface residual stress of the obtained manganese-cobalt-zinc-based ferrite must be less than 40 MPa. Here, the value of surface residual stress is based on the (551) surface peak appearing at 148.40° by X-ray diffraction, assuming that the surface of manganese-cobalt-zinc-based ferrite (ferrite core) is MnFe ₂ O ₄ . The displacement of the calculated micro-stress results.

Since manganese-cobalt-zinc ferrite is a brittle material, it will break due to tensile stress. Similarly, among glass that is a brittle material, there is known a tempered glass in which a compressive stress is applied to the surface in advance in order to cancel the tensile stress that causes the fracture. Inspired by this, the inventors of the present invention considered whether the fracture toughness value of the ferrite core could be improved by controlling the surface stress in the manganese-cobalt-zinc-based ferrite, and repeatedly studied. As a result, it was found that the tensile stress generated by the slight oxygen deficiency state caused by the reduction reaction during calcination remains on the surface of ordinary manganese-cobalt-zinc-based fertilizer granules, and by reducing the tensile stress, the manganese-cobalt material can be increased. Fracture toughness values of zinc-based ferritic iron. And there is a correlation between the fracture toughness value and the surface residual stress, in order to obtain 1.00MPa. The desired fracture toughness value of m ^1/2 or more requires that the surface residual stress be less than 40 MPa, preferably 38 MPa or less, and more preferably 36 MPa or less.

In order to keep the value of surface residual stress of manganese-cobalt-zinc-based fertilizer granules less than 40 MPa, it is necessary to immerse the calcined product after calcination in the production of ferrite cores in an oxidizing liquid with a concentration of 10 N or more for more than 0.50 hours. The dipping temperature is preferably in the range of 20°C to 60°C. The surface of the conventional manganese-cobalt-zinc-based ferrite iron will become a slight oxygen-deficient state due to the reduction effect during calcination, so tensile stress will be generated, and the surface residual stress will reach more than 40MPa. Therefore, in the manufacturing method of this invention, it is chemically oxidized by immersing the ferric iron which is a calcined product in the oxidizing liquid of predetermined density|concentration. By this method, oxygen was given to the surface portion of the ferrite iron, and as a result, the tensile stress on the surface was reduced, and the residual stress was less than 40 MPa.

Here, the oxidizing liquid is preferably nitric acid, sulfuric acid, or hydrochloric acid from the viewpoints of availability, ease of handling, and the like.

Next, the manufacturing method of the manganese-cobalt-zinc-based fertilizer granulated iron of the present invention will be described in detail. illustrate.

Regarding the production of manganese-cobalt-zinc-based ferrite iron, first, Fe ₂ O ₃ , ZnO, CoO and MnO are weighed so as to have a predetermined ratio, and these are thoroughly mixed and then pre-calcined and cooled to obtain pre-calcination. powder (pre-calcination step). _Fe2O3 , ZnO, _CoO and MnO are generally powders. When the pre-calcined powder is pulverized, additives as subcomponents defined in the present invention are added at a predetermined ratio, and mixed to obtain pulverized powder (mixing-pulverizing step). In this step, the powder is sufficiently homogenized so that there is no variation in the concentration of the added components, and the pre-calcined powder is miniaturized to the size of the target average particle diameter. An organic binder such as polyvinyl alcohol is added to the pulverized powder of the target composition thus obtained, and a granulated powder (granulation step) is produced through a granulation step by spray drying or the like. After the granulated powder is subjected to steps such as sieving, it is formed by applying pressure in a forming machine. After this molding, the calcination is carried out under appropriate calcination conditions (calcination step), and immersed in an oxidizing liquid having a concentration of 10 N or more for more than 0.50 hours, that is, more than 30 minutes (impregnation step). Then, if necessary, it is washed with water and dried to prepare a manganese-cobalt-zinc-based ferrite sintered body according to the present invention.

The obtained ferrite sintered body can be subjected to processing such as surface grinding.

The thus obtained manganese-cobalt-zinc-based ferric iron exhibits extremely excellent properties that cannot be achieved with conventional manganese-cobalt-zinc-based ferrites. These extremely excellent properties refer to the following extremely excellent properties: for example, the fracture toughness value of the flat sample measured by the fracture toughness based on JIS R1607 is 1.00 MPa. m ^1/2 or more (preferably 1.05MPa m ^1/2 or more), and the specific resistance is 30Ω. m or more (preferably 40Ω·m or more, more preferably 50Ω·m or more), the Curie temperature is 100°C or more, and the coercivity at 23°C of the annular core manufactured under the same conditions is 15.0A/m or less (preferably 13.0 A/m or less), and the value of the initial permeability at 23° C. and 10 MHz is 150 or more.

Example

(Example 1)

Using a ball mill, each raw material powder weighed so that the amounts of Fe ₂ O ₃ , ZnO, CoO and MnO were mixed for 16 hours so that the amounts of Fe 2 O 3 , ZnO, CoO and MnO were mixed for 16 hours, was pre-calcined at 900° C. for 3 hours in air, and was used in the air. Cool to room temperature for 1.5 hours to prepare pre-calcined powder. Next, SiO ₂ and CaO in equivalent amounts of 150 massppm and 700 massppm were weighed, respectively, and added to the pre-calcined powder, and pulverized by a ball mill for 12 hours. Next, polyvinyl alcohol was added to the pulverized powder obtained by the pulverization, spray-drying and granulation were performed, and a pressure of 118 MPa was applied to form a ring-shaped core shape and a flat-shaped core shape to prepare a molded body. Then, these shaped bodies were placed in a calcining furnace, and calcined at a maximum temperature of 1320° C. in a gas flow appropriately mixed with nitrogen and air for 2 hours. After being immersed in 13.0N (predetermined) nitric acid for 1.00 hours, it was taken out, washed with pure water, and dried to obtain a manganese-cobalt-zinc-based fertilizer granulated iron having an outer diameter: 25 mm, an inner diameter: 15 mm, and a height: 5 mm A sintered body annular core (hereinafter, also abbreviated as a ring core) and a sintered body flat core (hereinafter, also abbreviated as a rectangular parallelepiped core) having a length of 4 mm, a width of 35 mm, and a thickness of 3 mm.

In addition, high-purity raw materials are used as raw materials, and media such as ball mills are fully cleaned before use, so that the mixing of components from other materials is suppressed. Therefore, the contents of impurities P, B and Ti contained in the annular core and the cuboid core are respectively 4 massppm, 3 massppm and 15massppm. In addition, the content of P, B and Ti was quantified according to JIS K 0102 (inductively coupled plasma (ICP) mass spectrometry).

The initial permeability of the obtained toroidal core was calculated from the impedance and phase angle measured using an impedance analyzer (4294A manufactured by Keysight) by winding the toroidal core 10 times.

The coercivity Hc was measured at 23° C. based on JIS C 2560-2, and the specific resistance was measured by the four-terminal method.

The Curie temperature was calculated from the measurement result of the temperature characteristic of the inductance measured using an inductance capacitance and resistance meter (LCR meter) (4980A by Keysight).

The surface residual stress was calculated by the parallel-tilt method using a micro-stress measuring device (AuToMATE, manufactured by Rigaku), using Cr-Kα rays. At this time, assuming that the surface of the ferrite iron is MnFe ₂ O ₄ , the displacement of the (551) surface peak appearing at 148.40° was measured, and calculated using the values of the Paisson's ratio of 0.28 and the elastic constant of 147 GPa. In addition, the details of the above-mentioned parallel tilt method are described in <<Material>> (J.Soc.Mat.Sci., Japan), Vol.47, No.11, pp.1189-1194, Nov.1998.

Regarding the fracture toughness value of the rectangular parallelepiped core, in accordance with JIS R 1607, after applying a pre-crack to the central punched sample with a Vickers indenter, it fractured in a three-point bending test. size is calculated.

The obtained results are shown in Table 1, respectively.

As shown in this table, in Examples 1-1 to 1-7, which are examples of the invention, it is possible to obtain both a specific resistance of 30Ω. m or more, the coercivity at 23°C is 15.0A/m or less, the Curie temperature is 100°C or more, the initial permeability at 23°C and 10MHz is 150 or more, and the fracture toughness value is 1.00MPa. Better magnetic properties and high toughness of m ^1/2 .

On the other hand, in Comparative Examples 1-1 and 1-2 containing Fe ₂ O ₃ in an amount of 50.0 mol % or more, the specific resistance was greatly reduced, and the initial permeability at 10 MHz was also greatly deteriorated with an increase in eddy current loss. . On the other hand, in Comparative Example 1-3 in which the amount of Fe ₂ O ₃ was less than 45.0 mol %, although there was no problem in the specific resistance, since the magnetic anisotropy and the magnetostriction increased, the coercive force increased, and it was seen that to the drop in Curie temperature.

In Comparative Example 1-4 with excess ZnO, the Curie temperature was lowered to less than 100°C. On the other hand, in Comparative Example 1-5 in which ZnO was less than the predetermined range, the coercive force was increased and deviated from the desired range.

Focusing on CoO, in Comparative Examples 1 to 6 in which CoO was not added, the cancellation of the positive and negative magnetic anisotropy was insufficient, so the coercive force was improved. In Comparative Example 1-7 containing CoO, on the contrary, since the positive magnetic anisotropy was excessively high, the coercive force was increased, and the initial permeability at 10 MHz was also decreased.

(Example 2)

The raw materials were weighed so that Fe ₂ O ₃ was 49.0 mol %, CoO was 2.0 mol %, ZnO was 21.0 mol %, and MnO was 28.0 mol %. Preliminarily calcined at ℃ for 3 hours, and cooled to room temperature in the air for 1.5 hours to prepare precalcined powder. Next, SiO ₂ and CaO were added as auxiliary components in the amounts shown in Table 2 to the pre-calcined powder, and pulverized by a ball mill for 12 hours. Next, polyvinyl alcohol was added to the pulverized powder obtained by the pulverization, spray-drying and granulation were performed, and a pressure of 118 MPa was applied to form a ring-shaped core shape and a flat-shaped core shape to prepare a molded body. Then, these shaped bodies were placed in a calcining furnace, and calcined at a maximum temperature of 1320° C. in a gas flow appropriately mixed with nitrogen and air for 2 hours. After being immersed in 13.0N (predetermined) nitric acid for 1.00 hours, it was taken out, washed with pure water, and dried to obtain manganese-cobalt-zinc-based fertilizer granulated iron, outer diameter: 25 mm, inner diameter: 15 mm, height: 5 mm The sintered body annular core and the sintered body cuboid core with vertical: 4mm, horizontal: 35mm, thickness: 3mm. In addition, the contents of impurities P, B and Ti contained in the obtained annular core and the rectangular parallelepiped core were 4 massppm, 3 massppm and 15 massppm, respectively.

For each of the above-mentioned samples, the same method and apparatus as in Example 1 were used to evaluate each characteristic. The result of the obtained evaluation is shown in Table 2 together with the result of the said Example 1-2.

As shown in this table, in Examples 2-1 to 2-4 in which the amounts of SiO ₂ and CaO were within the prescribed ranges, a specific resistance of 30Ω was obtained. m or more, the coercive force at 23°C is 15.0 A/m or less, the Curie temperature is 100°C or more, and the initial permeability value at 23°C and 10 MHz is 150 or more, such as good magnetic properties and fracture toughness values. 1.00MPa. Such high toughness as m ^1/2 or more.

On the other hand, in Comparative Examples 2-1 and 2-3 in which only one of the two components, SiO ₂ and CaO, contained less than the predetermined amount, grain boundary formation was insufficient, specific resistance decreased, and grain growth was moderately suppressed Insufficient, so a part of low-strength coarse particles appear, so the fracture toughness value is lower than 1.00MPa. m ^1/2 . On the contrary, in Comparative Examples 2-2, 2-4, and 2-5 in which at least one of the same components was excessive, a plurality of magnetic properties represented by the initial permeability at 23° C. and 10 MHz due to the occurrence of abnormal particles Deterioration, in addition, the number of abnormal particles increased, and as a result, the fracture toughness value also decreased significantly.

(Example 3)

By the method shown in Example 1, a pressure of 118 MPa was applied to the granulated powder obtained by using various raw materials as follows, and it was formed into a ring-shaped core shape and a flat-shaped core. Table 3 shows the amount of unavoidable impurities contained in the raw material, and the basic components and auxiliary components are in the same proportions as in Example 1-2. Then, these shaped bodies were put into a calcining furnace, and calcined at a maximum temperature of 1320°C in a gas flow appropriately mixed with nitrogen and air for 2 hours, and these calcined calcined products were calcined at a room temperature of 23°C at a temperature of 13.0 After being immersed in nitric acid of N (predetermined) for 1.00 hours, it was taken out, washed with pure water and dried to obtain a manganese-cobalt-zinc-based ferrous sintered ring having an outer diameter: 25 mm, an inner diameter: 15 mm, and a height: 5 mm. A core and a sintered body cuboid core with a length: 4mm, a width: 35mm, and a thickness: 3mm.

For each of the above-mentioned samples, the same method and apparatus as in Example 1 were used to evaluate each characteristic. The result of the obtained evaluation is shown in Table 3 together with the result of the said Example 1-2.

As shown in this table, in Example 3-1 in which the unavoidable impurities P, B and Ti are within the predetermined ranges, not only the specific resistance, coercive force, and initial permeability at 23° C. and 10 MHz are all excellent, but also Also got 1.00MPa. Excellent fracture toughness values of m ^1/2 or more.

On the other hand, any one or more of the above-mentioned impurity components contains more than the predetermined In Comparative Examples 3-1 to 3-4 of the values, since abnormal particles appeared, many magnetic properties were deteriorated, and the fracture toughness value was also lowered, and the desired value was not obtained.

(Example 4)

A pressure of 118 MPa was applied to the granulated powder produced by the method shown in Example 1 and obtained by the same composition as in Example 1-2, and it was molded into a ring-shaped core shape and a flat-shaped core shape to obtain a molded body. Then, these compacts were placed in a calcining furnace, and sintered products obtained by calcining at a maximum temperature of 1320° C. for 2 hours in a gas flow appropriately mixed with nitrogen and air were obtained under the conditions shown in Table 4 as After being immersed in nitric acid, sulfuric acid, or hydrochloric acid of an oxidizing liquid, it was taken out, washed with pure water, and dried to obtain a sintered manganese-cobalt-zinc-based fertilizer with an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm. A body annular core and a sintered body cuboid core with a length: 4mm, a width: 35mm, and a thickness: 3mm. In addition, the amounts of P, B, and Ti components contained in the annular core and the cuboid core after immersion were 4 massppm, 3 massppm, and 15 massppm, respectively.

For each of the above-mentioned samples, the same method and apparatus as in Example 1 were used to evaluate each characteristic. The obtained result is shown in Table 4 together with the result of the said Example 1-2.

In Examples 4-1 to 4-8 produced under the conditions of the immersion step satisfying both of the following 1) and 2) in the immersion step, that is, 1) the concentration of the oxidizing liquid to be immersed was 10 prescribed (N) or more , and 2) the immersion time exceeds 0.50 hours (Hr)

The surface of the core, which is a manganese-cobalt-zinc-based ferrite, is chemically oxidized, so the surface residual stress of the core is less than 40 MPa. As a result, the tensile stress decreased, and the fracture toughness value of the obtained core was 1.00MPa. Good fracture toughness values above m ^1/2 .

On the other hand, in Comparative Examples 4-1 to 4-8 produced through the immersion step which did not satisfy the above-mentioned conditions, the chemical oxidation was insufficient, and thus the removal of the tensile stress remaining on the surface was insufficient. As a result, the desired fracture toughness value cannot be obtained.

Claims (3)

A manganese-cobalt-zinc fertilizer granule iron, comprising basic components, auxiliary components and inevitable impurities, wherein as the basic components, including: iron: calculated as Fe ₂ O ₃ conversion is more than 45.0mol% and less than 50.0mol%, Zinc: 15.5 mol % to 24.0 mol % in terms of ZnO, cobalt: 0.5 mol % to 4.0 mol % in terms of CoO, and manganese: the remainder, with respect to the above-mentioned basic components, as subcomponents, including: SiO ₂ : 50massppm~300massppm, and CaO: 300massppm~1300massppm, the amounts of P, B, and Ti in the unavoidable impurities are respectively suppressed to, P: less than 10massppm, B: less than 10massppm, and Ti: less than 50massppm, the said The value of surface residual stress of manganese-cobalt-zinc-based fertilizer granulated iron is less than 40MPa, and the fracture toughness value measured based on the fracture toughness of Japanese Industrial Standard R1607 is 1.00MPa. m ^1/2 or more, and the initial permeability at 23°C and 10MHz is more than 150, and the specific resistance is 30Ω. m or more, the coercive force at 23°C is 15.0 A/m or less, and the Curie temperature is 100°C or more. A method for producing manganese-cobalt-zinc-based fertilizer granulated iron, to obtain the manganese-cobalt-zinc-based fertilizer granulated iron as claimed in claim 1, comprising: a pre-calcination step, pre-calcining the mixture of the basic components, and cooling to obtain Pre-calcined powder; mixing-pulverization step, adding auxiliary components to the pre-calcined powder obtained in the pre-calcining step, and mixing and pulverizing to obtain pulverized powder; granulation step, adding to the pre-calcined powder obtained in the mixing-pulverization step A binder is added to the pulverized powder and mixed, followed by granulation; a calcination step, after the granulated powder obtained in the granulation step is shaped, and then calcined; and an impregnation step, immersed in an acid, and the In the impregnation step, the calcined product obtained in the calcination step is immersed in an oxidizing liquid with a concentration of 10 N or more for more than 0.50 hours. The method for producing manganese-cobalt-zinc-based fertilizer granulated iron according to claim 2, wherein the oxidizing liquid is nitric acid, sulfuric acid, or hydrochloric acid.