TW202030169A - MnCoZn ferrite and method for producing same - Google Patents

Abstract

Provided is MnCoZn ferrite which has: superior magnetic characteristics in terms of a high Curie temperature and a high specific resistance, and initial magnetic permeability at 23 DEG C and 10 Mhz, as well as low coercive force at 23 DEG C; and superior mechanical characteristics in terms of a high fracture toughness value as measured in compliance with JISR 1607 for a flat sample. The basic components and sub-components of the MnCoZn ferrite are adjusted to appropriate ranges, and amounts of P and B, which are unavoidable impurities, are suppressed to below 10 mass ppm for P and below 10 mass ppm for B, respectively. Furthermore, the number of voids in the crystal grain relative to the total number of voids in the MnCoZn ferrite is set to less than 55%; the initial magnetic permeability value of the MnCoZn ferrite at 23 DEG C and 10 MHz is set to 150 or more; the specific resistance is set to 30 [Omega].m or more; the coercive force at 23 DEG C is set to 15 A/m or less; the Curie temperature is set to 100 DEG C or more; and the fracture toughness as measured in compliance with JISR 1607 is set to 1.00 MPa.m1/2 or more.

Description

Manganese-cobalt-zinc fertilizer granular iron and its manufacturing method

The present invention relates to a manganese-cobalt-zinc (MnCoZn) ferrite grained iron which is particularly suitable for the magnetic core of automotive parts and its manufacturing method.

Manganese-zinc (MnZn) ferrous iron is a material widely used as a noise filter, transformer, or antenna core for switching power supplies. Its characteristics include soft magnetic materials, which have high magnetic permeability and low loss in the kHz region, and are inexpensive compared to amorphous metals.

On the other hand, ordinary manganese-zinc fertilizer grain iron has a low specific resistance, and it is difficult to maintain the permeability in the 10 MHz region due to attenuation caused by eddy current loss. As a countermeasure, it is known that the following manganese-cobalt-zinc-based fertilizer grain iron is selected to select a region where the Fe ₂ O ₃ content is less than 50 mol%, and to use Co ²⁺ ions that also show positive magnetic anisotropy instead of the usual manganese zinc It is the cancellation of the positive and negative magnetic anisotropy due to the presence of Fe ²⁺ ions with positive magnetic anisotropy in the fat iron. The manganese-cobalt-zinc fertilizer grain iron is characterized by high specific resistance and good initial permeability to the 10 MHz region.

However, high fracture toughness values are required as magnetic cores for electronic devices used in automobiles, the demand for which has been increasing in recent years with the hybridization and electrification of automobiles. This is because the oxide magnetic materials, including manganese-zinc-based ferrite, are ceramics, which are brittle materials, so they are prone to breakage. In addition, compared with conventional home appliance applications, they are subject to constant vibration in automotive applications. Continuous use in damaged environments. However, at the same time, in automotive applications, weight reduction and space saving are also required, so in addition to high fracture toughness values, it is important to have better magnetic properties at high temperatures.

As a manganese-zinc-based manganese iron for automobile installation, various developments have been advanced in the past. Patent Document 1 and Patent Document 2 have been reported as nutritious iron with good magnetic properties, and Patent Document 3 and Patent Document 4 are reported as manganese-zinc-based nutritious iron with improved fracture toughness value. Furthermore, as high-resistance manganese-cobalt-zinc-based ferrous iron that maintains the initial permeability to the 10 MHz region, Patent Document 5 and Patent Document 6, etc. have been reported. [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 Laid-Open No. 2005-179092 [Patent Document 6] Japanese Patent Laid-Open No. 2005-247651

[Problem to be Solved by the Invention] Generally, in order to increase the initial permeability of the existing manganese-zinc-based ferrous iron, it is effective to reduce the magnetic anisotropy and magnetostriction. In order to achieve this, it is necessary to set the blending amounts of Fe ₂ O ₃ , ZnO, and MnO, which are main components of manganese-zinc-based fertilizer grain iron, in an appropriate range. In addition, by applying sufficient heat in the calcination step, the grains in the ferrous iron are grown appropriately, and the movement of the magnetic wall in the grains in the magnetization step is facilitated, and the segregated components at the grain boundaries are added to produce The grain boundary of moderate and uniform thickness maintains the specific resistance and suppresses the attenuation of the initial permeability accompanying the increase in frequency, achieving high initial permeability in the 100 kHz region. However, the highest specific resistance of manganese-zinc fertilizer grain iron is only about 20 Ω·m, and it is impossible to maintain the initial permeability to 10 MHz. Therefore, the manganese-cobalt-zinc-based fertilizer grain iron is sometimes used.

On the other hand, in addition to the above-mentioned magnetic properties, magnetic cores of electronic parts for automobiles require a high fracture toughness value in order not to be damaged even in an environment subject to constant vibration. If the manganese-zinc-based ferrite as the magnetic core is damaged, the inductance is greatly reduced, so the electronic parts cannot achieve the desired effect, and the entire car cannot be operated due to its influence. Based on the above, the manganese-cobalt-zinc-based ferrous iron used in automotive electronic parts is required to have both good magnetic properties represented by high initial permeability and high fracture toughness values.

However, in Patent Document 1 and Patent Document 2, although the composition for achieving desired magnetic properties is mentioned, the fracture toughness value is not described at all. Similarly, in Patent Document 5 and Patent Document 6, no fracture toughness value is involved, and it is considered that it is not suitable as a magnetic core for automotive electronic parts. On the other hand, in Patent Document 3 and Patent Document 4, although improvement of the fracture toughness value is mentioned, the magnetic properties are insufficient as a magnetic core of an electronic component for automobiles, and it is still not suitable for the application.

Therefore, the object of the present invention is to provide a manganese-cobalt-zinc-based ferrite having an initial permeability value of 150 or more at 23°C and 10 MHz, a specific resistance of 30 Ω·m or more, and a coercivity at 23°C. The force is 15 A/m or less, and the Curie temperature is 100°C or more. It also has excellent magnetic properties such as flat specimens. The fracture toughness value measured in accordance with Japanese Industrial Standards (JIS) R 1607 is 1.00 Excellent mechanical properties such as MPa·m ^1/2 or more. [Means to solve the problem]

Therefore, the inventors first studied Fe ₂ O ₃ , CoO, and ZnO, which are the basic components of manganese-cobalt-zinc-based ferrite that can achieve high initial permeability at 23°C and 10 MHz in toroidal cores. The appropriate amount was studied. As a result, within this composition range, Fe ²⁺ ions, which are the cause of the decrease in electrical resistance, are hardly contained. Therefore, a certain degree of high specific resistance can be maintained, and the magnetic anisotropy and magnetostriction are small. It was found that a low coercivity important as a soft magnetic material, a high Curie temperature that is not a practical problem, and an appropriate range for maintaining a basic component of high initial permeability in the 10 MHz region can be realized.

Next, SiO ₂ and CaO, which are non-magnetic components segregating at the grain boundaries, were added in appropriate amounts as secondary components to form grain boundaries of uniform thickness. As a result, it was found that not only the specific resistance is further increased, but also the crystal structure can be adjusted.

In addition to these, the inventors investigated the factors that are effective in increasing the fracture toughness value. According to the analysis of the image observed after grinding and etching the fracture surface of the manganese-cobalt-zinc-based fertilizer grain iron, they found voids in the material. There is a correlation between the ratio of voids remaining in the crystal grains and the fracture toughness value. That is, voids sometimes exist in the grain boundaries and sometimes in the crystal grains, but by reducing the voids remaining in the crystal grains (hereinafter also referred to as intra-grain voids), the manganese-cobalt-zinc fertilizer grains are brittle materials The propagation of iron cracks was suppressed, and as a result, it was found that the fracture toughness value of the material increased.

From this point of view, the inventors conducted further investigations and discovered two methods for reducing voids in the crystal grains. First of all, the grain growth balance is broken during the sintering of ferrite iron, and abnormal particles sometimes appear, but the abnormal particles contain a lot of voids in the crystal grains. In order to suppress the generation of such abnormal particles and reduce the number of voids in the crystal grains, it is necessary to reduce the inevitable impurity content. Furthermore, since the appearance of abnormal particles increases the loss, it is also required to avoid abnormal particles from the viewpoint of magnetic properties. The other is the following method: in the production of normal manganese-cobalt-zinc-based ferrous iron, through a pre-calcination step, by appropriately controlling the maximum temperature of the pre-calcination at this time, and the cooling rate or atmosphere to prevent excessive material It absorbs oxygen and reduces the amount of oxygen released during the reduction reaction during calcination, thereby reducing the occurrence of voids and reducing the voids in the crystal grains. By properly controlling these two methods, the fracture toughness value of the material can be improved.

As described above, adjusting the amounts of Fe ₂ O ₃ , CoO, and ZnO as the basic components, and the amounts of SiO ₂ and CaO as the non-magnetic components to an appropriate amount while reducing the voids in the crystal grains is to obtain the desired magnetic properties. It is necessary for manganese-cobalt-zinc fertilizer grained iron with high fracture toughness value. Furthermore, in the aforementioned Patent Document 1 and Patent Document 2, the fracture toughness value is not mentioned, and this improvement can be said to be impossible. Similarly, Patent Document 5 and Patent Document 6 mention good magnetic properties, but the fracture toughness value is still 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, the desired magnetic properties cannot be achieved. Therefore, it is impossible to produce manganese-cobalt-zinc-based ferrous iron suitable for magnetic cores of electronic parts for automobiles that are practically useful based on these findings. The present invention is based on the above knowledge.

That is, the gist of the present invention is configured as follows. 1. A manganese-cobalt-zinc-based fertilizer grain iron comprising basic components, auxiliary components and unavoidable impurities, wherein the basic components are iron, zinc, cobalt, and manganese in terms of Fe ₂ O ₃ , ZnO, CoO, and MnO The total of is set to 100 mol%, iron: 45.0 mol% or more and less than 50.0 mol% in terms of Fe ₂ O ₃ , zinc: 15.5 mol% to 24.0 mol% in terms of ZnO, and cobalt: calculated as CoO 0.5 mol% to 4.0 mol% and manganese: the remainder, relative to the basic components, the side components are SiO ₂ : 50 massppm to 300 massppm and CaO: 300 massppm to 1300 massppm, and the inevitable The amounts of P and B in the impurities are respectively suppressed to P: less than 10 massppm, B: less than 10 massppm, and the number of voids in the crystal grains is less than 55% relative to the total number of voids in the manganese-cobalt-zinc-based ferrous iron. The initial permeability at 23°C and 10 MHz is 150 or more, the specific resistance is 30 Ω·m or more, the coercivity at 23°C is 15 A/m or less, and the Curie temperature is 100°C or more, measured in accordance with JIS R 1607 The fracture toughness value of 1.00 MPa·m ^1/2 or more.

2. A manufacturing method of manganese-cobalt-zinc-based fertilizer grain iron, which is to obtain the manganese-cobalt-zinc-based fertilizer grain iron described in 1 above, comprising: A pre-calcining step, pre-calcining the mixture of the basic components and cooling to obtain pre-calcined powder; In a mixing-pulverization step, the auxiliary components are added to the pre-calcined powder, mixed and pulverized to obtain pulverized powder; In the granulation step, a binder is added to the pulverized powder and mixed, and then granulated to obtain granulated powder; A forming step of forming the granulated powder to obtain a formed body; and The calcining step, calcining the shaped body to obtain manganese-cobalt-zinc fertilizer grain iron, The highest temperature of pre-calcination in the pre-calcination step is in the range of 800°C to 950°C, In addition, at least one of the cooling rate from the maximum temperature to 100°C of 800°C/hr or more, or the oxygen concentration of the atmosphere during cooling from the maximum temperature to 100°C of 5 vol% or less is satisfied.

3. A manufacturing method of manganese-cobalt-zinc-based fertilizer iron, which is the manufacturing method of manganese-cobalt-zinc-based fertilizer iron to obtain the manganese-cobalt-zinc-based fertilizer iron described in 1 or 2, comprising: a pre-calcining step, The mixture of the basic components is pre-calcined and cooled to obtain pre-calcined powder; a mixing-pulverizing step: adding the auxiliary components to the pre-calcined powder, mixing and pulverizing to obtain pulverized powder; granulating step , After adding a binder to the pulverized powder and mixing them, granulation is performed to obtain granulated powder; a forming step of forming the granulated powder to obtain a formed body; and a calcining step of calcining the formed body, The manganese-cobalt-zinc-based fertilizer grain iron is obtained, and the peak intensity ratio (X) shown by the following (1) formula of the pre-calcined powder is 1.00 or more, X=(spinel analyzed by X-ray diffraction method Peak intensity of compound)/(peak intensity of α-Fe ₂ O ₃ analyzed by X-ray diffraction method)...(1).

4. The method for producing manganese-cobalt-zinc-based ferrous iron as described in 3, wherein the maximum temperature of the pre-calcination in the pre-calcination step is in the range of 800°C to 950°C, In addition, at least any one of the cooling rate from the maximum temperature to 100° C. being 800° C./hr or more or the oxygen concentration of the atmosphere during cooling from the maximum temperature to 100° C. being 5 vol% or less is satisfied. [Effects of the invention]

The manganese-cobalt-zinc fertilizer grain iron of the present invention has an initial permeability of 150 or more at 23°C and 10 MHz, a specific resistance of 30 Ω·m or more, and a coercivity of 15 A/m or less at 23°C. The inner temperature is 100°C or higher, which has excellent magnetic properties, and the flat sample has excellent mechanical properties of 1.00 MPa·m ^1/2 or more in the fracture toughness value measured in accordance with JIS R 1607.

Hereinafter, the present invention will be specifically described. In addition, in this specification, the numerical range represented by "-" refers to the range including the numerical value described before and after "-" as the lower limit and the upper limit. First, in the present invention, the reason why the composition of manganese-cobalt-zinc-based fat iron (hereinafter also referred to simply as fat iron) is limited to the above-mentioned range will be explained. In addition, all of the iron, zinc, cobalt, and manganese contained in the present invention as basic components are expressed in terms of Fe ₂ O ₃ , ZnO, CoO, and MnO. In addition, with regard to the content of these Fe ₂ O ₃ , ZnO, CoO, and MnO, the total amount of iron, zinc, cobalt, and manganese in terms of Fe ₂ O ₃ , ZnO, CoO, and MnO is 100 mol% (mol %) means mol%. On the other hand, the content of side components and unavoidable impurities is expressed in mass ppm (massppm) relative to the basic components.

Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%. When Fe ₂ O ₃ is contained excessively, the amount of Fe ²⁺ increases, thereby reducing the specific resistance of the manganese-cobalt-zinc-based fertilizer grain iron. In order to avoid this, it is necessary to suppress the Fe ₂ O ₃ amount to less than 50 mol%. However, if it is too small, the coercive force will increase and the Curie temperature will decrease, so the minimum content of iron is 45.0 mol% in terms of Fe ₂ O ₃ . The content of Fe ₂ O ₃ is preferably at least 47.1 mol% and less than 50.0 mol%, more preferably in the range of 47.1 mol% to 49.5 mol%.

ZnO: 15.5 mol%～24.0 mol% ZnO increases the saturation magnetization of the fat iron and has a relatively low saturated vapor pressure, so it has the effect of increasing the sintering density and is an effective ingredient for reducing the coercivity. Therefore, it is assumed to contain at least 15.5 mol% of zinc 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, zinc is 24.0 mol% or less in terms of ZnO. The preferred range of ZnO is 15.5 mol% to 23.0 mol%, more preferably 17.0 mol% to 23.0 mol%.

CoO: 0.5 mol%～4.0 mol% Co ²⁺ ions in CoO are ions with positive magnetic anisotropy energy. With the addition of a reasonable amount of CoO, the absolute value of the sum of the magnetic anisotropy energy decreases, and the result is realized This reduces the coercivity. Therefore, more than 0.5 mol% of CoO must be added. On the other hand, a large amount of addition results in a decrease in specific resistance, initiation of abnormal particle growth, and an excessively positive total of the magnetic anisotropy energy, which instead leads to an increase in coercive force. In order to prevent this, it is assumed that the addition of CoO is limited to a maximum of 4.0 mol%. A preferable range of CoO is 1.0 mol% to 3.5 mol%, and a more preferable range of CoO is 1.0 mol% to 3.0 mol%.

MnO: remaining part The present invention is manganese-cobalt-zinc fertilizer grain iron, and the remaining part of the basic components needs to be MnO. The reason is that if the remaining part is not MnO, good magnetic characteristics represented by low coercivity and high permeability at 10 MHz cannot be obtained. The preferred range of MnO is 26.5 mol% to 32.0 mol%. The content of MnO is more preferably 26.0 mol% to 32.0 mol%, and still more preferably 25.0 mol% to 32.0 mol%.

The basic components have been described above, but the subsidiary components are as follows. SiO ₂ : 50 massppm～300 massppm It is known that SiO ₂ contributes to the homogenization of the crystalline structure of ferrous iron. With appropriate addition, it reduces the number of grain voids remaining in the crystal grains, thereby reducing the coercive force and also Can improve the fracture toughness value. Therefore, at least 50 massppm of SiO ₂ should be contained. On the other hand, in the case of excessive addition, abnormal particles will appear instead, which will significantly reduce the fracture toughness value, while the initial permeability and coercivity at 10 MHz will also be significantly degraded, so the content of SiO ₂ is required Limited to less than 300 massppm. The content of SiO ₂ is preferably in the range of 60 massppm to 250 massppm.

Cao: 300 massppm～1300 massppm CaO has the effect of segregating at the grain boundaries of manganese-cobalt-zinc fertilizer grain iron and inhibiting grain growth, and has the effect of reducing the number of voids in the grains. Therefore, with an appropriate amount of addition, the specific resistance increases, the coercivity also decreases, and the fracture toughness value can also be increased. Therefore, the minimum content of CaO is 300 massppm. On the other hand, if the addition amount 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 content of CaO is preferably 350 massppm to 1200 massppm, more preferably 350 massppm to 1000 massppm.

Next, description will be made on the inevitable impurities that are suppressed. P: less than 10 massppm, B: less than 10 massppm P and B are components unavoidably contained mainly in raw iron oxide. If the content is very small, there is no problem. However, if the content is more than a certain level, abnormal grain iron growth occurs, and the intra-grain porosity increases, so the fracture toughness value decreases and the coercivity The increase in force and the decrease in initial permeability have serious adverse effects. Therefore, the contents of P and B are both suppressed to less than 10 massppm. Preferably, both P and B are 8 massppm or less.

In addition, not limited to the composition, the properties of manganese-cobalt-zinc-based ferrous iron are greatly affected by various parameters. Therefore, in the present invention, in order to ensure better magnetic properties and strength properties, the following regulations are set. Fracture toughness value measured in accordance with JIS R 1607: 1.00 MPa·m ^1/2 or more manganese-cobalt-zinc-based fertilizer grain iron is a ceramic, brittle material, and therefore hardly undergoes plastic deformation. Therefore, the fracture toughness value is measured by the Single-Edge-Precracked-Beam method (SEPB method) specified in JIS R 1607. In the SEPB method, a Vickers indentation is formed in the center of a flat sample, and a bending test is performed in a state where a pre-crack is applied to measure the fracture toughness value. The manganese-cobalt-zinc-based ferrous iron of the present invention is assumed to be used in automobiles requiring high toughness, and the fracture toughness value is required to be 1.00 MPa·m ^1/2 or more. In order to satisfy this condition, in the manganese-cobalt-zinc-based ferrous iron produced by powder molding, voids remain in the material. However, after grinding the fractured surface and etching the grain boundary with fluoronitric acid, the temperature is between 200 and 500 To analyze the image observed under the magnification field of view, it is necessary to divide the total number of intra-grain voids by the total number of remaining voids in the field of view, and the intra-grain void ratio must be less than 55%. The void ratio in the crystal grains is preferably 50% or less, more preferably 47% or less. This is because the cracks in the manganese-cobalt-zinc-based ferrous iron mainly propagate along the intra-grain voids. Therefore, when the intra-grain porosity is high, the cracks easily propagate and the toughness value is low, so it cannot satisfy 1.00 MPa·m ^{1 /2} or more.

In order to keep the intra-grain void ratio less than 55%, two conditions must be met. First, the amounts of P and B, which are unavoidable impurities, are suppressed to less than 10 massppm. This is because these components induce the appearance of abnormal particles containing a large number of intra-grain voids and increase the intra-grain void ratio.

Secondly, the pre-calcination conditions in the manufacturing step of manganese-cobalt-zinc-based ferrous iron are optimized. Basically, the calcination of manganese-cobalt-zinc-based fertilizer grain iron as a metal oxide is a reduction reaction, during which excess oxygen held by the material is released. In the molding step before calcination, in order to maintain the shape of the compressed powder compact, an organic binder is added to the molded granulated powder, and the binder is burned and decomposed and removed in the initial stage of calcination. The reducing atmosphere at the time of decomposition and removal may be accompanied by a chemical reaction that deprives oxygen from the ferrous iron material as an oxide, and this chemical reaction is accompanied by volume expansion, which may damage the molded body. Therefore, in order to prevent this, in the calcination step, the manganese-cobalt-zinc-based fertilizer particles are intentionally made to absorb and retain oxygen in excess of the stoichiometric ratio. However, of course in the case of excessively maintaining oxygen, the amount of oxygen released during calcination will increase. As the grains grow during sintering, oxygen is released to the outside of the material, but the more oxygen is released, the more the voids in the grains increase. When the voids in the grains reach 55% or more, the fracture toughness value will be lower. It is 1.00 MPa·m ^1/2 as desired. Therefore, the pre-calcining step needs to process manganese-cobalt-zinc-based ferritic iron in an appropriate temperature and atmosphere range. Specifically, the treatment needs to be carried out under the following conditions, that is, the maximum temperature of the pre-calcination is in the range of 800°C to 950°C (preferably in the range of 850°C to 950°C), and the maximum temperature to 100°C is satisfied. The cooling rate is 800° C./h or higher, or the oxygen concentration during cooling from the maximum temperature to 100° C. is at least any of 5 vol% or lower (preferably 4 vol% or lower). Furthermore, it is preferable that the maximum temperature of pre-calcination when the oxygen concentration during cooling from the maximum temperature to 100°C is 5 vol% or less is 800°C to 950°C (more preferably, 850°C to 930°C), and the pre-calcining atmosphere in the air.

In addition, the amount of oxygen retained by the pre-calcined powder can be quantified by X-ray diffraction (XRD) analysis using Cu-Kα rays with a wavelength of 1.542 Å. For the processing, the peak intensity ratio (X) shown in the following formula (1) may be 1.00 or more. The peak intensity ratio (X) is preferably 1.1 or more. X=(peak intensity of spinel compound analyzed by X-ray diffraction method)/(peak intensity of α-Fe ₂ O ₃ analyzed by X-ray diffraction method)...(1) The formula (1) This means that when using Cu-Kα rays with a wavelength of 1.542 Å for XRD analysis, the peak intensity of the spinel compound appearing at about 35° among the peaks appearing is divided by the peak intensity of α-Fe ₂ O ₃ appearing at 33° On the other hand, if the ratio is 1.00 or more, the intra-grain void ratio decreases, and a good toughness value can be obtained.

Next, the manufacturing method of the manganese-cobalt-zinc-based fertilizer grain iron of the present invention will be described. In the production of manganese-cobalt-zinc-based ferrous iron, first, the basic components of Fe ₂ O ₃ , ZnO, CoO, and MnO powder are weighed in such a ratio as described above, and these are thoroughly mixed to form a mixture , And then pre-calcin the mixture (pre-calcin step). At this time, in order to have both better magnetic properties and fracture toughness values, in addition to setting the maximum temperature of pre-calcination in the range of 800°C to 950°C, it also satisfies the cooling rate from the maximum temperature to 100°C of 800°C/ When the oxygen partial pressure during cooling from the highest temperature to 100℃ is at least one of h or more, or less than 5%, when the pre-calcined powder is analyzed by XRD using Cu-Kα rays with a wavelength of 1.542 Å, it appears at about 35° The ratio of the peak intensity of the spinel compound divided by the peak intensity of α-Fe ₂ O ₃ appearing at 33° is 1.00 or more, preferably 1.1 or more. Furthermore, here, the spinel compound refers to a compound having a spinel crystal structure existing in the ferrite pre-calcined powder, and is represented by the general formula AFe ₂ O ₄ (A is Mn, Zn).

Next, to the obtained calcined powder, the auxiliary components are added at a predetermined ratio so as to have the above content, and are mixed with the pre-calcined powder to be pulverized (mixing-pulverization step). In this step, the powder is sufficiently homogenized so that the concentration of the added component is not biased, and at the same time, the pre-calcined powder is refined to the size of the target average particle size to prepare pulverized powder. Next, a well-known organic binder such as polyvinyl alcohol is added to the pulverized powder, and it is granulated by a spray drying method or the like to obtain granulated powder (granulation step). Then, as necessary, through steps such as sieving for particle size adjustment, pressure is applied in a molding machine and molded to form a molded body (molding step). Next, the molded body is calcined under known calcining conditions to obtain manganese-cobalt-zinc-based ferrous iron (calcination step). The obtained manganese-cobalt-zinc-based fertilizer grain iron can be processed appropriately such as surface polishing.

The manganese-cobalt-zinc-based ferrous iron obtained in this way not only has the following excellent magnetic properties, that is, the value of the initial permeability at 23°C and 10 MHz is 150 or more, preferably 160 or more, and more preferably 170 Above, the specific resistance is 30 Ω·m or more, preferably 40 Ω·m or more, more preferably 50 Ω·m or more, and the coercivity at 23°C is 15 A/m or less, preferably 13 A/m Below, the Curie temperature is 100°C or higher, and the flat sample has a fracture toughness value of 1.00 MPa·m ^1/2 or more, which cannot be achieved by conventional manganese-cobalt-zinc-based ferrous iron, as measured in accordance with JIS R 1607. The mechanical characteristics. Example

(Example 1) Using a ball mill, the raw material powders weighed so that the amounts of Fe ₂ O ₃ , ZnO, CoO and MnO become the ratios shown in Table 1 were mixed for 16 hours, and then pre-calcined in air at 900°C for 3 hours . Furthermore, the cooling atmosphere from the maximum temperature of pre-calcination to 100°C is in air, and the cooling rate is 1600°C/h. Next, SiO ₂ and CaO corresponding to 150 massppm and 700 massppm were weighed, respectively, and then added to the pre-calcined powder, and pulverized by a ball mill for 12 hours. Next, polyvinyl alcohol is added to the obtained pulverized powder, spray-dried and granulated, and a pressure of 118 MPa is applied to form an annular core and a flat core. Then, these formed bodies were put into a calcining furnace, and calcined in a gas stream suitably mixed with nitrogen and air at a maximum temperature of 1350°C for 2 hours to obtain outer diameter: 25 mm, inner diameter: 15 mm, and height: 5 mm The sintered body annular core and the longitudinal: 4 mm, the transverse: 35 mm, the thickness: 3 mm sintered body flat core (also called cuboid core). In addition, high-purity raw materials are used as raw materials, and media such as ball mills are sufficiently cleaned before use to prevent the mixing of components from other materials. Therefore, the inevitable impurities contained in the ring core and the rectangular parallelepiped core are the amounts of P and B, respectively 4 massppm and 3 massppm. Furthermore, the contents of P and B were quantified in accordance with JIS K 0102 (Ion pair chromatography (IPC) mass analysis method).

The initial permeability of the toroidal core obtained was obtained by winding 10 turns on the toroidal core, and was calculated based on the impedance and the phase angle measured using an impedance analyzer (4294A manufactured by Keysight). The coercivity Hc is measured at 23°C based on JIS C 2560-2, and the specific resistance is measured by the four-terminal method. The Curie temperature is calculated based on the measurement results of the temperature characteristics of the inductor measured using an inductance capacitance and resistance meter (LCR meter) (4980A manufactured by Keysight). Regarding the intra-grain porosity, the obtained annular core was fractured, the fractured surface was polished and then etched with fluoronitric acid, and then observed with an optical microscope at a magnification of 500 times. It was counted that it appeared in a visual field of 120 μm in length and 160 μm in width. Calculated by dividing the number of voids in the grain by the total number of voids. The peak intensity ratio of the pre-calcined powder is the XRD analysis of the pre-calcined powder using Cu-Kα rays with a wavelength of 1.542 Å (Ultima IV manufactured by Rigaku), and the spines appearing at about 35° It is calculated by dividing the peak intensity of the stone compound by the peak intensity of α-Fe ₂ O ₃ appearing at 33°. Regarding the fracture toughness value of the rectangular parallelepiped core, based on JIS R 1607, a Vickers indenter is used to pre-crack the sample punched in the center, and then it fractures in a three-point bending test. The size is calculated. The results obtained are shown in Table 1.

[Table 1] Table 1 Basic composition of ferrite Pre-calcined powder Fertilizer iron characteristics Fe ₂ O ₃ amount ZnO amount CoO amount MnO amount Peak intensity ratio Porosity in grain Fracture toughness value Kic Initial permeability (23℃, 10 MHz) Specific resistance Coercivity Curie temperature mol% mol% mol% mol% - % MPa・m ^1/2 - Ω·m A/m °C Example 1-1 49.5 21.0 3.0 26.5 1.32 35 1.15 190 50 7.3 130 Example 1-2 49.0 21.0 2.0 28.0 1.37 37 1.13 220 130 7.5 120 Example 1-3 47.1 21.0 2.0 29.9 1.41 40 1.11 210 350 12.6 110 Example 1-4 49.0 23.0 2.0 26.0 1.40 38 1.12 220 140 7.1 100 Example 1-5 49.0 17.0 2.0 32.0 1.33 36 1.14 170 120 8.4 130 Example 1-6 49.0 21.0 1.0 29.0 1.36 38 1.12 210 130 8.6 120 Example 1-7 49.0 21.0 3.5 26.5 1.39 37 1.13 170 120 9.2 130 Comparative example 1-1 51.0 21.0 2.0 26.0 1.19 32 1.16 10 0.1 6.2 140 Comparative example 1-2 50.0 21.0 2.0 27.0 1.23 34 1.15 10 0.1 6.6 130 Comparative example 1-3 44.0 21.0 2.0 33.0 1.46 43 1.09 160 430 16.0 90 Comparative example 1-4 49.0 25.0 2.0 24.0 1.43 46 1.08 180 140 6.3 90 Comparative example 1-5 49.0 15.0 2.0 34.0 1.27 33 1.16 160 120 15.8 170 Comparative example 1-6 49.0 21.0 0.0 30.0 1.34 36 1.14 190 120 18.8 120 Comparative example 1-7 49.0 21.0 5.0 25.0 1.39 37 1.13 130 120 24.0 130 ※The underline indicates outside the proper scope of the present invention.

As shown in the table, in Examples 1-1 to 1-7, which are examples of the invention, a specific resistance of 30 Ω·m or more and a coercivity at 23°C of 15 A/m or less can be obtained. The inner temperature is 100°C or higher, 23°C, and 10 MHz. The initial permeability value is 150 or higher, and the fracture toughness value is 1.00 MPa·m ^1/2 or higher. It has better magnetic properties and high toughness. In contrast, in Comparative Example 1-1 and Comparative Example 1-2 containing Fe ₂ O ₃ at 50.0 mol% or more, the specific resistance is greatly reduced, and the initial permeability of 10 MHz with the increase in eddy current loss is also large. Amplitude degradation. On the other hand, in Comparative Examples 1-3 in which Fe ₂ O _{3 is} less than 45.0 mol%, it is found that although high toughness can be achieved, since the magnetic anisotropy and magnetostriction become larger, the coercive force increases and the Curie The temperature drops. In Comparative Examples 1-4 with excess ZnO, the Curie temperature was lowered to less than 100°C. In contrast, in Comparative Examples 1-5 in which ZnO is less than the proper range, the coercive force rises and deviates from the desired range. Focusing on CoO, in Comparative Examples 1-6 with a small amount of CoO, the cancellation of the positive and negative magnetic anisotropy was insufficient, so the coercive force was increased. In addition, in Comparative Examples 1-7, which contained excessive amounts, the positive magnetic The anisotropy increases excessively, so the coercivity increases, and the initial permeability at 10 MHz also decreases.

(Example 2) The raw materials were weighed so that Fe ₂ O ₃ was 49.0 mol%, ZnO was 21.0 mol%, CoO was 2.0 mol%, and MnO was 28.0 mol%. After mixing the raw materials for 16 hours using a ball mill, Pre-calcined in air at 900°C for 3 hours. Furthermore, the cooling atmosphere from the maximum temperature of pre-calcination to 100°C is in air, and the cooling rate is 1600°C/h. Next, SiO ₂ and CaO in the amounts shown in Table 2 were added to the pre-calcined powder, and pulverized by a ball mill for 12 hours. Next, polyvinyl alcohol is added to the obtained pulverized powder, spray-dried and granulated, and a pressure of 118 MPa is applied to form an annular core and a flat core. Then, these formed bodies were put into a calcining furnace, and calcined in a gas stream suitably mixed with nitrogen and air at a maximum temperature of 1320°C for 2 hours to obtain outer diameter: 25 mm, inner diameter: 15 mm, and height: 5 mm The sintered body ring core and the sintered body cuboid core with length: 4 mm, width: 35 mm, and thickness: 3 mm. In addition, the amounts of P and B, which are inevitable impurities contained in the obtained annular core and rectangular parallelepiped core, were 4 massppm and 3 massppm, respectively. For each sample, the same method and apparatus as in Example 1 were used to evaluate the characteristics of each. The results obtained are listed in Table 2.

[Table 2] Table 2 Fertilizer iron secondary component Pre-calcined powder Fertilizer iron characteristics SiO ₂ amount CaO amount Peak intensity ratio Porosity in grain Fracture toughness value Kic Initial permeability (23℃, 10 MHz) Specific resistance Coercivity Curie temperature massppm massppm - % MPa·m ^1/2 - Ω·m A/m °C Example 1-2 150 700 1.37 37 1.13 220 130 7.5 120 Example 2-1 60 800 1.36 36 1.15 210 90 6.9 120 Example 2-2 250 450 1.37 39 1.12 210 140 9.3 120 Example 2-3 200 350 1.37 38 1.12 210 120 8.8 120 Example 2-4 150 1000 1.36 36 1.14 230 180 6.5 120 Comparative example 2-1 40 700 1.35 59 0.95 220 20 7.7 120 Comparative example 2-2 320 700 1.37 68 0.92 130 10 16.3 120 Comparative example 2-3 150 250 1.36 60 0.96 220 20 8.1 120 Comparative example 2-4 150 1500 1.37 68 0.91 120 20 17.4 120 Comparative example 2-5 320 1500 1.36 73 0.85 100 10 18.1 120 ※The underline indicates outside the proper scope of the present invention.

As shown in the table, in the examples in which the amounts of SiO ₂ and CaO are within the specified range, in 2-1 to 2-4, a coercive force with a specific resistance of 30 Ω·m or more and 23°C can be obtained. 15 A/m or less, Curie temperature of 100°C or higher, 23°C, 10 MHz, the value of initial permeability is 150 or higher, which has good magnetic properties and fracture toughness value of 1.00 MPa·m ^1/2 or higher The high toughness. In contrast, in Comparative Examples 2-1 and 2-3 in which one of the two components, SiO ₂ and CaO, only contained less than the specified amount, the grain boundary formation was insufficient, so the specific resistance was lowered. The fracture toughness value decreases due to the increase in the intra-grain void ratio. On the contrary, even if there is too much comparative example 2-2, comparative example 2-4 and comparative example 2-5 in the same composition, due to the appearance of abnormal particles, the initial permeability at 23°C and 10 MHz is representative In addition, the abnormal particles contain a large number of voids in many crystal grains, so the intra-grain porosity increases, and as a result, the fracture toughness value is also greatly reduced.

(Example 3) By the method shown in Example 1, a granulated powder obtained by using the following raw materials was obtained in which the basic components and auxiliary components had the same composition ratio as in Example 1-2. On the other hand, The amounts of P and B contained as inevitable impurities vary. A pressure of 118 MPa was applied to the granulated powder to form an annular core and a flat core. Then, these formed bodies were put into a calcining furnace, and calcined in a gas stream suitably mixed with nitrogen and air at a maximum temperature of 1320°C for 2 hours to obtain outer diameter: 25 mm, inner diameter: 15 mm, and height: 5 mm The sintered body ring core and the sintered body cuboid core with length: 4 mm, width: 35 mm, and thickness: 3 mm. With respect to each of the samples, the same method and device as in Example 1 were used to evaluate their characteristics. The results obtained are shown in Table 3.

[Table 3] Table 3 Fertile iron impurities Pre-calcined powder Fertilizer iron characteristics P amount B amount Peak intensity ratio Porosity in grain Fracture toughness value Kic Initial permeability (23℃, 10 MHz) Specific resistance Coercivity Curie temperature massppm massppm - % MPa·m ^1/2 - Ω·m A/m °C Example 1-2 4 3 1.37 37 1.13 220 130 7.5 120 Example 3-1 8 8 1.36 43 1.06 190 60 9.8 120 Comparative example 3-1 15 3 1.35 63 0.92 130 10 16.8 120 Comparative example 3-2 4 15 1.35 66 0.89 110 20 16.3 120 Comparative example 3-3 15 15 1.36 88 0.74 50 10 27.1 120 ※The underline indicates outside the proper scope of the present invention.

As shown in the table, in Example 3-1 where the amounts of P and B, which are inevitable impurities, are within the specified range, not only the specific resistance, coercivity, and initial permeability at 23°C and 10 MHz are all Excellent, and an excellent fracture toughness value of 1.00 MPa·m ^1/2 or more was obtained. In contrast, in Comparative Examples 3-1, 3-2, and 3-3 in which one or both of the two components contained a predetermined value or more, abnormal particles appeared, so many magnetic properties were deteriorated, and the intra-grain porosity It also increased, so the fracture toughness value also decreased, and neither the initial permeability nor the fracture toughness value obtained the desired value.

(Example 4) Except that the heat treatment temperature, cooling rate, and cooling atmosphere of the preliminary calcination step were changed to the conditions shown in Table 4, granulated powder was produced in the same manner as in Example 1-2. A pressure of 118 MPa was applied to the granulated powder to form an annular core and a flat core. Then, these formed bodies were put into a calcining furnace, and calcined in a gas stream suitably mixed with nitrogen and air at a maximum temperature of 1320°C for 2 hours to obtain outer diameter: 25 mm, inner diameter: 15 mm, and height: 5 mm sintered body ring core and sintered body rectangular core with length: 4 mm, width: 35 mm, thickness: 3 mm. With respect to each of the samples, the same method and device as in Example 1 were used to evaluate their characteristics. The results obtained are shown in Table 4 together.

[Table 4] Table 4 Pre-calcining conditions Pre-calcined powder Fertilizer iron characteristics Maximum temperature of pre-calcination Atmosphere during pre-calcination Cooling rate after pre-calcination (maximum temperature~100℃) Oxygen concentration (vol%) during cooling after pre-calcination (maximum temperature ~100℃) Peak intensity ratio Porosity in grain Fracture toughness value Kic Initial permeability (23℃, 10 MHz) Specific resistance Coercivity Curie temperature °C - ℃/h % - % MPa·m ^1/2 - Ω·m A/m °C Example 1-2 900 air 1600 20.6 1.37 37 1.13 220 130 7.5 120 Example 4-1 900 air 800 20.6 1.11 46 1.08 210 130 7.6 120 Example 4-2 900 air 800 5.0 1.23 40 1.11 210 130 7.5 120 Example 4-3 900 air 400 5.0 1.15 43 1.10 210 130 7.4 120 Example 4-4 900 air 200 0.01 1.33 38 1.12 220 130 7.5 120 Example 4-5 950 air 1700 20.6 1.43 34 1.15 240 140 7.8 120 Example 4-6 800 air 1400 20.6 1.25 39 1.12 220 120 7.3 120 Comparative example 4-1 900 air 600 20.6 0.95 57 0.98 210 130 7.3 120 Comparative example 4-2 900 air 400 20.6 0.82 61 0.97 210 130 7.2 120 Comparative example 4-3 900 air 400 10.0 0.86 61 0.95 200 130 7.5 120 Comparative example 4-4 900 air 200 10.0 0.68 68 0.89 210 140 7.5 120 Comparative example 4-5 975 air 1800 20.6 1.48 33 1.16 130 140 9.3 120 Comparative example 4-6 750 air 1300 20.6 0.86 60 0.95 200 110 9.8 120 Comparative example 4-7 975 air 200 0.01 1.59 31 1.16 120 140 10.5 120 Comparative example 4-8 750 air 200 0.01 0.94 59 0.96 180 110 11.3 120 ※The underline indicates outside the proper scope of the present invention.

In the pre-calcining step, 1) the maximum temperature is within the range of 800°C to 950°C and 2) the cooling rate from the maximum temperature to 100°C is 800°C/h or more, or the oxygen during cooling from the maximum temperature to 100°C In Examples 4-1 to 4-6 prepared under the condition of at least any one of the concentration of 5% by volume or less, since the excess oxygen absorption during cooling can be suppressed, the spinel compound/α-Fe ₂ O observed by XRD The peak ratio of ₃ was maintained at 1.0 or more, and the amount of oxygen released during firing was reduced, so the intra-grain void ratio was reduced. As a result, a good fracture toughness value of 1.00 MPa·m ^1/2 or more was obtained. In contrast, in Comparative Examples 4-1 to 4-8 produced outside the above range, in 4-1 to 4-4, 4-6, and 4-8, the spinel compound in the preliminary calcination step If the amount of produced is insufficient or the amount of oxygen absorption during cooling increases, the amount of α-Fe ₂ O ₃ in the obtained pre-calcined powder increases. Therefore, the amount of oxygen released during firing increases, and the void ratio within the crystal grains increases. As a result, the fracture toughness value is lower than the expected value. Focusing on Comparative Examples 4-5 and 4-7 in which the pre-calcination temperature exceeds the appropriate range, the fracture toughness value is high, and on the other hand, the initial permeability at 23° C. and 10 MHz deteriorates. This is because excessive heat is applied during the pre-calcination, and the reaction proceeds excessively, and the particle size of the pre-calcined powder becomes coarse and hardened. Therefore, it cannot be sufficiently crushed in the subsequent crushing step. Therefore, the sintering reaction between the powders occurs during the calcination. It is hindered and insufficient, so it is considered that the desired magnetic properties cannot be obtained.

Claims (4)

A manganese-cobalt-zinc-based fertilizer grain iron, including basic components, auxiliary components and unavoidable impurities, wherein the basic components will be the total of iron, zinc, cobalt, and manganese in terms of Fe ₂ O ₃ , ZnO, CoO, and MnO Set to 100 mol%, iron: 45.0 mol% or more and less than 50.0 mol% in terms of Fe ₂ O ₃ , zinc: 15.5 mol% to 24.0 mol% in terms of ZnO, cobalt: 0.5 mol in terms of CoO %～4.0 mol% and manganese: the remainder, relative to the basic components, the side components are SiO ₂ : 50 massppm to 300 massppm and CaO: 300 massppm to 1300 massppm, and the inevitable impurities The amounts of P and B are respectively suppressed to P: less than 10 massppm, B: less than 10 massppm, and the number of voids in the crystal grains is less than 55% relative to the total voids of the manganese-cobalt-zinc-based fertilizer grain iron, and then at 23°C , The initial permeability at 10 MHz is 150 or more, the specific resistance is 30 Ω·m or more, the coercivity at 23°C is 15 A/m or less, and the Curie temperature is 100°C or more, measured according to Japanese Industrial Standard R 1607 The fracture toughness value of 1.00 MPa·m ^1/2 or more. A method for manufacturing manganese-cobalt-zinc-based fertilizer grain iron is to obtain the manganese-cobalt-zinc-based fertilizer grain iron as described in claim 1, comprising: A pre-calcining step, pre-calcining the mixture of the basic components and cooling to obtain pre-calcined powder; In a mixing-pulverization step, the auxiliary components are added to the pre-calcined powder, mixed and pulverized to obtain pulverized powder; In the granulation step, a binder is added to the pulverized powder and mixed, and then granulated to obtain granulated powder; A forming step of forming the granulated powder to obtain a formed body; and The calcining step, calcining the shaped body to obtain manganese-cobalt-zinc fertilizer grain iron, The highest temperature of pre-calcination in the pre-calcination step is in the range of 800°C to 950°C, In addition, at least one of the cooling rate from the maximum temperature to 100°C of 800°C/hr or more, or the oxygen concentration of the atmosphere during cooling from the maximum temperature to 100°C of 5 vol% or less is satisfied. A method for manufacturing manganese-cobalt-zinc-based fertilizer grain iron is to obtain the manganese-cobalt-zinc-based fertilizer grain iron as described in claim 1 or 2, comprising: a pre-calcining step, The mixture of the basic components is pre-calcined and cooled to obtain pre-calcined powder; a mixing-pulverization step, adding the auxiliary components to the pre-calcined powder, and mixing and pulverizing to obtain pulverized powder; granulating step, After adding and mixing a binder to the pulverized powder, granulation is performed to obtain a granulated powder; a forming step of forming the granulated powder to obtain a formed body; and a calcining step of calcining the formed body to obtain Manganese-cobalt-zinc-based fertilizer grain iron, the peak intensity ratio (X) shown by the following (1) formula of the pre-calcined powder is 1.00 or more, X=(Spinel compound analyzed by X-ray diffraction method Peak intensity)/(peak intensity of α-Fe ₂ O ₃ analyzed by X-ray diffraction method)...(1). The method for producing manganese-cobalt-zinc-based ferrous iron as described in claim 3, wherein The maximum temperature of the pre-calcination in the pre-calcination step is in the range of 800°C to 950°C, In addition, at least any one of the cooling rate from the maximum temperature to 100° C. being 800° C./hr or more or the oxygen concentration of the atmosphere during cooling from the maximum temperature to 100° C. being 5 vol% or less is satisfied.