Magnetic core

Abstract

To provide a magnetic core having improved reliability.SOLUTION: The magnetic core includes 37 to 44 mol% of manganese (Mn), 9 to 16 mol% of zinc (Zn), 42 to 52 mol % of iron (Fe), a magnetic additive, and a non-magnetic additive. The magnetic core has a permeability of 2,900 or more, and a core loss of 500 mW / cm3 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a magnetic core with better reliability.

Background Art

[0002] Recently, due to the continuous concern for the environment and regulations, research on vehicles equipped with electric motors has been actively carried out, and the market is also showing a trend of expansion. Therefore, the importance of the vehicle power electronics (PE) field is also increasing together.

[0003] Typical vehicle power electronic components include a DC-DC converter. In a vehicle using an electric motor as a power source, a high-voltage battery for driving the electric motor and an auxiliary battery for supplying power to electrical loads are usually provided together, and the auxiliary battery can be charged by the power of the high-voltage battery. For charging the auxiliary battery, it is necessary to convert the DC power of the high-voltage battery into a DC power corresponding to the voltage of the auxiliary battery, and for this purpose, a DC-DC converter can be used.

[0004] A DC-DC converter converts a DC power into an AC power, then steps up or down the voltage through a transformer, and further rectifies it to output a DC power of a desired output voltage. Therefore, passive elements such as inductors operating at high frequencies are built in.

[0005] However, generally, the magnetic cores constituting inductors or transformers have problems in that it is difficult to meet the reliability required in the vehicle environment, such as low-temperature characteristics or thermal shock.

[0006] Also, recently, the trend of slimming down components has also affected magnetic elements. However, since the slimmed magnetic elements have relatively smaller size and surface area, they are disadvantageous in terms of heat capacity and heat dissipation. Therefore, it is also necessary to consider a method of reducing heat generation so as to reduce losses.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The technical problem to be achieved by the present invention is to provide a more reliable magnetic core.

[0008] In particular, an object of the present invention is to provide a magnetic core having excellent low-temperature characteristics and thermal shock characteristics.

[0009] The technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understandable to those with ordinary knowledge in the technical field to which the present invention belongs from the following description.

Means for Solving the Problems

[0010] The magnetic core according to one embodiment includes manganese (Mn) with a molar ratio of 37 to 44 mol%, zinc (Zn) with a molar ratio of 9 to 16, iron (Fe) with a molar ratio of 42 to 52, a magnetic additive, and a non-magnetic additive, and has a magnetic permeability of 2,900 or more and a core loss of 500 mW / cm 3 as follows.

[0011] For example, the magnetic core can have a magnetic permeability reduction rate of 4 to 9% and a core loss increase rate of 0.5 to 7% under the conditions of 1000 cycles of 30 minutes each at -40 to 125 °C.

[0012] For example, the magnetic core can have a magnetic permeability reduction rate of 2 to 5% and a core loss increase rate of 0.05 to 3.00% under the impact of a half-sine wave shock acceleration of 100 G in each of the ± directions of the x-axis, y-axis, and z-axis for 6 ms.

[0013] For example, the magnetic core can have a magnetic permeability reduction rate of 1 to 3% and a core loss increase rate of 0.2 to 1.0% after maintaining vibration for 4 hours for each of the x-axis, y-axis, and z-axis at a vibration frequency of 10⇔2000 Hz, a vibration acceleration of 5 G, 20 minutes per reciprocation.

[0014] For example, the magnetic core has a toroidal shape, and after applying an imprint acceleration of 30 mm / min five times in the vertically downward direction along the height direction of the toroidal shape with a limit load of 1000 N, it can have a breaking load of 800 N or more on average.

[0015] For example, the magnetic additive of the magnetic core can include cobalt (Co) and nickel (Ni).

[0016] For example, the magnetic core can contain cobalt in a molar ratio of 0.1 to 1 and nickel in a molar ratio of 0.1 to 0.5.

[0017] For example, the non-magnetic additive of the magnetic core can include at least one of silicon (Si), calcium (Ca), tantalum (Ta), vanadium (V), and zirconium (Zr).

[0018] For example, the magnetic core can have a content of 50 to 200 ppm of silicon, 200 to 700 ppm of calcium, 200 to 900 ppm of tantalum, 50 to 500 ppm of vanadium, and 50 to 500 ppm of zirconium, respectively.

[0019] Also, the magnetic core according to an embodiment includes a magnetic compound containing manganese (Mn) with a molar ratio of 37 to 44 mol%, zinc (Zn) with a molar ratio of 9 to 16, iron (Fe) with a molar ratio of 42 to 52, cobalt (Co) with a molar ratio of 0.1 to 1, nickel (Ni) with a molar ratio of 0.1 to 0.5, and an additive. The magnetic compound includes a plurality of crystal grains and grain boundaries between the plurality of crystal grains. The ratio of the content of cobalt at the center of the first crystal grain to the content of cobalt at the center of the first grain boundary located between the first crystal grain and the second crystal grain adjacent to the first crystal grain among the plurality of crystal grains is 0.4 or more.

[0020] For example, the content of cobalt can gradually decrease from the first crystal grain to the first grain boundary.

[0021] For example, among the plurality of crystal grains, the ratio of the content of nickel at the center of the third crystal grain to the content of nickel at the center of the second grain boundary located between the third crystal grain and the fourth crystal grain adjacent to the third crystal grain can be 0.4 or more.

[0022] For example, the additive can include a non-magnetic material.

[0023] For example, the additive can include four or more of silicon (Si), calcium (Ca), tantalum (Ta), vanadium (V), niobium (Nb), and zirconium (Zr).

[0024] For example, the silicon can have a content of 50 to 200 ppm, the calcium can have a content of 200 to 700 ppm, the tantalum can have a content of 200 to 900 ppm, the vanadium can have a content of 50 to 500 ppm, and the zirconium can have a content of 50 to 500 ppm, respectively.

[0025] Also, a magnetic core according to an embodiment includes manganese (Mn) with a molar ratio of 37 to 44, zinc (Zn) with a molar ratio of 9 to 16, iron (Fe) with a molar ratio of 42 to 52, and a magnetic compound containing a non-magnetic additive. The non-magnetic additive includes SiO2 with a content of 50 to 200 ppm, CaO with a content of 200 to 700 ppm, Ta2O5 with a content of 200 to 900 ppm, ZrO2 with a content of 50 to 500 ppm, and V2O5 with a content of 50 to 500 ppm. The magnetic compound includes a plurality of crystal grains and grain boundaries between the plurality of crystal grains. The content of at least one kind of the non-magnetic additive gradually increases from the center of the first crystal grain in the first direction to the second crystal grain adjacent to the first crystal grain among the plurality of crystal grains, and the ratio of the total content of at least one kind of the non-magnetic additive in the first crystal grain to the total content of the at least one kind of the non-magnetic additive at the first grain boundary between the first crystal grain and the second crystal grain is 0.1 or more.

[0026] For example, the magnetic core can further include at least one magnetic additive of cobalt (Co) and nickel (Ni).

[0027] For example, the cobalt can have a molar ratio of 0.1 to 1, and the nickel can have a molar ratio of 0.1 to 0.5.

[0028] For example, the ratio of the content of cobalt at the center of the first crystal grain to the content of cobalt at the center of the first crystal grain boundary can be 0.4.

[0029] For example, the ratio of the content of nickel at the center of the first crystal grain to the content of nickel at the center of the first crystal grain boundary can be 0.4.

[0030] Also, the magnetic core according to an embodiment includes manganese (Mn) with a molar ratio of 37 to 44, zinc (Zn) with a molar ratio of 9 to 16, iron (Fe) with a molar ratio of 42 to 52, and a compound containing an additive, and the additive can include at least three elements within Groups 4 and 5 of the periodic table.

[0031] For example, the elements within Group 5 can include two or more of tantalum (Ta), vanadium (V), and niobium (Nb).

[0032] For example, the elements within Group 4 can include at least one of zirconium (Zr) and titanium (Ti).

[0033] For example, the total content of the elements within Group 4 and Group 5 can be 1500 ppm or less.

[0034] For example, the additive can further include at least three of cobalt (Co), nickel (Ni), silicon (Si), and calcium (Ca).

[0035] For example, the additive can include an oxide.

[0036] For example, the additive can include 50 to 200 ppm of SiO2, 200 to 700 ppm of CaO, 200 to 900 ppm of Ta2O5, 50 to 500 ppm of ZrO2, and 50 to 500 ppm of V2O5.

[0037] For example, the compound includes a plurality of crystal grains and grain boundaries between each of the plurality of crystal grains. The compound includes a non-magnetic additive, and the content of at least one type of the non-magnetic additive gradually increases from the center of the first crystal grain in the first direction to the second crystal grain adjacent to the first crystal grain among the plurality of crystal grains. The ratio of the sum of the content of at least one type of the non-magnetic additive in the first crystal grain to the sum of the content of the at least one type of the non-magnetic additive at the first grain boundary between the first crystal grain and the second crystal grain can be 0.1 or more.

Advantages of the Invention

[0038] The magnetic core according to the embodiment can have excellent low-temperature characteristics and thermal shock characteristics together with an improved composition ratio of grain boundaries.

[0039] The effects obtained by the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understandable to those with ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9a

Figure 9b

Figure 9c

Embodiments for Carrying Out the Invention

[0041] The present invention can be subjected to various modifications and can have various embodiments, but specific embodiments will be described based on the drawings. However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0042] Terms including ordinal numbers such as second and first can be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, within the scope not departing from the scope of the rights of the present invention, the second component can be named the first component, and similarly, the first component can also be named the second component. The term "and / or" includes a combination of a plurality of related described items or any one of the plurality of related described items.

[0043] When one component is referred to as being "coupled" or "connected" to another component, it should be understood that it can be directly coupled or connected to the other component, but other components can also be present therebetween. On the other hand, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that no other components are present therebetween.

[0044] In the description of the embodiments, the description that each layer (film), region, pattern or structure is formed "on" or "under" a substrate, each layer (film), region, pad or pattern includes all those formed directly or with other layers interposed therebetween. The reference for above or below each layer is determined based on the drawings. Also, in the drawings, the thickness or size of each layer (film), region, pattern or structure can be deformed for the clarity and convenience of the description, and thus does not fully reflect the actual size.

[0045] The terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as "including" or "having" are intended to specify the presence of the features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and should not be construed as precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0046] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be construed to have a meaning consistent with the meaning in the context of the related art, and should not be construed in an ideal or overly formal sense unless clearly defined in this application.

[0047] According to one embodiment, it is proposed to enhance the ratio of a specific metal element within the grain boundaries so that the magnetic core has better reliability.

[0048] FIG. 1 shows an example of the bonding form of the substances constituting the magnetic core according to one embodiment. FIG. 1 shows an enlarged shape of a cross-section 11 of a toroidal magnetic core 10.

[0049] Referring to FIG. 1, the substances constituting the magnetic core 10 according to the embodiment include solid portions 21, 22 grown from crystal nuclei, that is, crystal grains or particles (grains), and crystal grain boundaries or grain boundaries (grain boundaries) corresponding to the boundaries 31 of the respective particles 21, 22. In a general core, the content of the main composition substance in the grain boundary 31 is low, and relatively, the content of the main composition substance in the particles 21, 22 is high. However, in the magnetic core according to this embodiment, at least a part of the content ratio of the main composition substance can also be increased in the grain boundary 31 to have excellent reliability.

[0050] For this reason, different from the general core manufacturing process in which additives are initially blended with the main composition substance, in this embodiment, at least a part of the additives can be mixed after the mixing and sintering processes of the main composition substance.

[0051] Hereinafter, the main composition substance and additives according to this embodiment will be described first, and then the manufacturing process will be explained.

[0052] The main composition of the magnetic core according to one embodiment can have a content ratio as shown in Table 1 below.

Table 1

[0053] Referring to Table 1, the magnetic core according to an embodiment can include cobalt oxide (CoO) and nickel oxide (NiO) as magnetic additives, along with manganese (Mn), zinc (Zn), and iron (Fe) as the main components. The content ratios in Table 1 are based on molar ratios (mol%), and the experimental results of combining characteristics after converting to weight ratios (wt%) are as shown in Table 2 below.

Table 2

[0054] Table 2 shows the experimental results where the Fe content was fixed at approximately 71% for Samples 1 to 4 and approximately 67% for Samples 5 to 8, and the sintering conditions were made the same for each other with the additives described below excluded.

[0055] First, in the case of Samples 1 to 4, the content was changed in such a way that the Mn content was increased and the Zn content was decreased from Sample 1 to Sample 4. Based on the loss, it can be seen that the optimal condition is Sample 3. That is, the performance improves when Mn is 20 wt% or more and Zn is 8.56 wt% or less.

[0056] Also, in the case of Samples 5 to 8, the content was changed in such a way that the Mn content was increased and the Zn content was decreased from Sample 5 to Sample 8. Based on the loss, it can be seen that Zn shows good performance at 4.3 to 12.83 wt%, and Sample 6 with 8.56 wt% is the most optimal. In the case of Mn, it can be seen that the performance deteriorates when the Zn ratio is excessively reduced from 28.2 wt% or more.

Table 3

[0057] Ultimately, when the Fe2O3 is around 70 wt% as shown in Table 3 above, from the perspective of loss, the Zn content is preferably 6 wt% or more.

[0058] Next, the non-magnetic additives will be described with reference to Table 4 below.

Table 4

[0059] Referring to Table 4, in addition to the main compositions described above, the magnetic core according to the embodiment can include at least one non-magnetic additive such as silicon oxide (SiO2), calcium oxide (CaO), tantalum pentoxide (Ta2O5), zirconium dioxide (ZrO2), and vanadium pentoxide (V2O5). Such non-magnetic additives can play a role in maintaining the bonding force between the main constituent substances after the heat treatment (i.e., sintering) described later.

[0060] A manufacturing method according to an embodiment using each substance shown in Tables 1 to 4 will be described with reference to FIG. 2.

[0061] FIG. 2 is a flowchart showing an example of the manufacturing process of a magnetic core according to an embodiment.

[0062] Referring to FIG. 2, first, the Fe2O3, MnO, ZnO, CoO, and NiO powders prepared as raw materials (i.e., main constituent substances) can be mixed with each other (S210). Here, the purity of each raw material is preferably 99% or more, and the powder particle size is preferably 10 μm or less, but is not necessarily limited thereto. For example, a ball mill can be used in this process. The amount of balls can be 2.5 times the mass of the raw materials, and it can be performed at 24 rpm for 18 hours.

[0063] Next, in order to improve the density of the spherical granules in the spray drying (S250) process described later, a calcination process can be performed on the mixed raw material powder (S220). For example, this process can be performed by raising the temperature at a rate of 3.5 °C / min to a maximum of 950 °C and maintaining it for 4 hours, but is not necessarily limited thereto.

[0064] Subsequently, since powders that have generally undergone a calcination process often agglomerate with each other, a crushing process can be performed to minimize the particle size (S230). Here, constituent substances other than the raw materials, i.e., non-magnetic additives such as SiO, CaO, Ta2O5, ZrO2, V2O5, etc., can be mixed in this process. A ball mill can be used for this process, but it is not necessarily limited to this.

[0065] Subsequently, a slurry to be sprayed in the subsequent spray drying (S250) process can be produced (S240). This process can be carried out by stirring a solvent, a binder, and a binder dispersant together with the product of the S230 stage. For example, the solvent can be distilled water, the binder can be polyvinyl alcohol corresponding to 1 wt% of the product of the S230 stage, the binder dispersant can have a content of 0.1 - 0.3 wt% of the product of the S230 stage, and the stirring time is preferably 10 hours or more, but it is not necessarily limited to this.

[0066] The produced slurry can be granulated (granulation, spherical) through a spray drying process (S250). This process improves the flowability of the powder by granulation so that high-pressure molding can be performed in the next molding (S260) stage. This is because the higher the pressure during molding, the higher the density of the product and the better the magnetic properties.

[0067] The particles granulated by spray drying can be molded at high pressure according to the desired shape (S260). For example, the desired shape can include toroidal type, E type, EPC type, I type, etc., depending on the application, and the pressure can be 3 - 5 tons per unit area, but it is not necessarily limited to this.

[0068] Once the molding is completed, a sintering process can be performed to ensure the desired core performance (S270). For example, this process can be carried out by maintaining the maximum temperature of 1360°C for 4 hours, but it is not necessarily limited to this.

[0069] After sintering, a surface finishing (polishing) process for component application can be performed (S280).

[0070] Among the processes described so far, compared with general processes, there is the greatest difference at the time of mixing non-magnetic additives that are not the main composition substance. In other words, in general processes, the main composition substance and non-magnetic additives are mixed together at the first mixing, but in the process according to this embodiment, after the mixing, calcination and crushing of the raw materials, non-magnetic additives can be mixed in. The process according to such an embodiment can be called a 'post-addition process'.

[0071] Also, according to another embodiment, the post-addition process can be performed in two steps. For example, as described above, after the mixing, calcination and crushing of the raw materials, 92% - 96% of the non-magnetic additives are added, and the remaining non-magnetic additives (that is, 4% - 8% depending on the previous addition amount) can be added during the spray drying (S250) process. In such a case, more additives can be distributed at the grain boundaries.

[0072] The effects of the post-addition process will be described based on FIG. 3 and Table 5.

[0073] FIG. 3 is a diagram for explaining the effects of the post-addition process according to the embodiment.

[0074] FIG. 3 shows the magnetic permeability and loss according to the respective temperatures when the post-addition process of the embodiment is applied and when a general process (referred to as an 'existing process') is applied.

[0075] The sintering conditions, the main composition ratio (that is, Fe 69.75 wt%, Mn 22.94 wt%, Zn 6.97 wt%), and the additive content (Si 100 ppm, Ca 500 ppm, Ta 500 ppm, Zr 100 ppm, V 100 ppm, Co 2,000 ppm, Ni 200 ppm) are fixed for both the post-addition process and the existing process. However, Co and Ni introduced after the mixing, calcination and crushing of the raw materials in the post-addition process are 10% of the corresponding additive amounts.

[0076] In FIG. 3, based on 25° C. and -30° C., the numerical values of loss and magnetic permeability are as shown in Table 5 below.

Table 5

[0077] Considering FIG. 3 and Table 5 comprehensively, it can be seen that when the subsequent process is applied compared with the existing process, both the loss and the magnetic permeability are improved (i.e., the improvement of low-temperature characteristics), especially in the low-temperature situation (here, -30° C.).

[0078] On the other hand, the functions of each composition substance in the above-described process are as follows.

[0079] First, when SiO2 is 200 ppm or more, it can induce grain growth (Flowing through the grain boundary) and cause excessive grain growth.

[0080] Non-magnetic additives (SiO2, CaO, Ta2O5, Nb2O5, ZrO2) can commonly contribute to the reduction of hysteresis loss. For example, Ta2O5 can help CaO to be well distributed at the grain boundary. Here, Ta2O5 can be replaced by Nb2O5 or ZrO2 (i.e., (SiO2 + CaO) + (Ta2O5, Nb2O5, ZrO2)).

[0081] In addition, non-magnetic additives also contribute to the reduction of eddy current loss. Specifically, since the probability of CaO existing at the grain boundary is high, it precipitates at the grain boundary and increases the resistivity of the grain boundary. Also, V2O5 can form a liquid film at the grain boundary to suppress grain growth. Further, Ta2O5 can perform the functions of increasing the resistivity and suppressing excessive grain growth due to the addition of SiO2.

[0082] On the other hand, Co 2+ is replaced instead of Fe 2+ and can contribute to the control of magnetic anisotropy by improving the temperature dependence of the magnetic permeability.

[0083] In addition, by substituting NiO for ZnO, the relative content of Fe2O3 can be increased, and the temperature at which the minimum core loss occurs can be shifted to a higher temperature.

[0084] In addition, by being present at the grain boundaries, CaO has the effect of reducing the hysteresis loss as described above, and can also improve the high frequency response.

[0085] The additive effects of the additives such as Si, Zr, and Ta described above will be explained based on FIG. 4 and Table 6. FIG. 4 is a diagram for explaining the effects of the additives according to the examples.

[0086] In FIG. 4, in order to more clearly show the additive effects of the additives, a general process (that is, mixing the main composition material and the non-magnetic additive together during the initial mixing), rather than the above-described post-addition process (that is, after the mixing, calcination, and crushing of the raw materials, the non-magnetic additive is mixed in), was applied, and the sintering process and the main composition ratio (that is, Fe 70.7 wt%, Mn 23.17 wt%, Zn 6.13 wt%) were fixed for each situation.

[0087] Referring to FIG. 4, the experiments were conducted for three situations: i) the situation without adding additives, ii) the situation with the addition of Co and Ni, and iii) the situation with the addition of Si, Zr, and Ta to Co and Ni.

[0088] The loss and permeability numerical values based on 25 °C in FIG. 4 are as shown in Table 6 below.

Table 6

[0089] Taking FIGS. 4 and 6 together, it can be seen that in terms of both permeability and loss, the situation with the addition of Si, Zr, and Ta to Co and Ni shows the best performance.

[0090] Hereinafter, the optimal content of the composition material according to an embodiment will be described.

[0091] First, the experimental conditions related to the Ni content are as follows.

[0092] The Ni content is changed to 200 ppm, 400 ppm, and 600 ppm. For each case, the sintering process is the same, with the main composition being Fe 71.13 wt%, Mn 21.76 wt%, Zn 7.11 wt%, and the additive content fixed at Co 3000 ppm, Si 100 ppm, Ca 300 ppm, Ta 500 ppm. The experimental results under such conditions are as shown in Fig. 5.

[0093] Fig. 5 shows an example of the variation patterns of the magnetic permeability and loss with the nickel content of the magnetic core according to the examples.

[0094] Referring to Fig. 5, for both the magnetic permeability and the loss, similar results appeared when Ni was 200 ppm and 400 ppm. However, when Ni was 600 ppm, there was a significant difference not only in the magnetic permeability but also in the overall shape of the graph, especially from the perspective of loss. This can mean that 600 ppm of Ni is in an over-added state. Therefore, it is preferable that the Ni content is less than 600 ppm, but it is not necessarily limited to this.

[0095] Next, the experimental conditions related to the Co content are as follows.

[0096] The Co content is changed to two cases of 500 ppm and 1500 ppm. In both cases, it is mixed with 200 ppm of Ni by the post-treatment process described above, and the sintering process is the same, with the main composition being Fe 69.75 wt%, Mn 22.94 wt%, Zn 6.97 wt%, and the additive content fixed at Si 100 ppm, Ca 500 ppm, Ta 500 ppm, Zr 100 ppm, V 100 ppm. The experimental results under such conditions are as shown in Fig. 6.

[0097] Fig. 6 shows an example of the variation patterns of the magnetic permeability and loss with the cobalt content of the magnetic core according to the examples.

[0098] Referring to FIG. 6, it can be seen that when Co is 1500 ppm, it exhibits better magnetic permeability and loss characteristics than when it is 500 ppm. However, when Co is 500 ppm, it can be seen that there is a section where, depending on the temperature, the performance is worse in the existing process rather than the subsequent process. Therefore, the content of Co is preferably at least more than 500 ppm, but is not necessarily limited thereto.

[0099] To verify the optimal content of the composition material according to this example, while keeping the content of some of the main composition materials fixed, the content of the remaining main composition materials and non-magnetic additives was varied in various ways, and the characteristics measured under the conditions of 100 kHz and 200 mT are shown in Table 7 below.

Table 7

[0100] In Table 7, among the main compositions, manganese (Mn) has a content of 22.94 wt%, zinc (Zn) has a content of 6.97 wt%, and iron (Fe) has a content of 69.75 wt%. Except for the case where some additives are removed, the contents (ppm) of SiO, CaO, Ta2O5, ZrO2, and V2O5 are also fixed. As a result of experiments while changing the contents of CoO and NiO under such conditions, when the content of CoO is 3000 ppm and the content of NiO is 400 ppm, a magnetic permeability of 3349 and a loss value of 349 appeared. Such contents correspond to 0.3 wt% for CoO and 0.004 wt% for NiO by weight ratio. Since the highest magnetic permeability and the minimum loss appeared together compared to other cases, it can be seen that there is a critical meaning at the corresponding content ratio.

[0101] Hereinafter, in Table 7, the performance of the magnetic core manufactured by the process of FIG. 2 with the content when the content of CoO is 3000 ppm and the content of NiO is 400 ppm will be described. The performance of the magnetic core described below is assumed to be applied to vehicle parts, and will be described by the experimental results based on AEC-Q200 among the reliability items for vehicles. AEC-Q200 is a standard applied to passive components among the reliability test specifications prepared by the Automotive Electronic Council (AEC).

[0102] Specifically, the test items were respectively carried out for thermal shock, impact resistance, vibration and strength.

[0103] First, the thermal shock test was carried out for 1000 cycles (each cycle for 30 minutes) under the conditions of -40 / +125 °C corresponding to Grade 1 of AEC-Q200. The form of temperature change applied in this test is as shown in Figure 7. As shown in the figure, in this test, each cycle maintains the temperature at -40 °C for 30 minutes and at +125 °C for 30 minutes respectively, and the temperature conversion is carried out linearly over 5 minutes.

[0104] The test results are as shown in Table 8 below.

Table 8

[0105] As shown in Table 8, the experimental results show that the permeability reduction is 5.0 - 8.2%, the increase in core loss (@100 °C) is 0.8 - 6.7%, and the results meet the AEC-Q200 Pass condition (that is, within ±15%) without cracks and fractures.

[0106] Next, for the impact resistance test item, a total of 18 tests were carried out, 3 times for each of the + / - directions of the x / y / z axes respectively, with a maximum impact acceleration of 100 G for a half-sine wave impact waveform and a time of 6 ms. The test results are as shown in Table 9 below.

Table 9

[0107] As shown in Table 9, the experimental results show that the permeability reduction is 2.3 - 4.5%, the maximum increase in core loss (@100 °C) is 2.4%, and the results meet the AEC-Q200 Pass condition without cracks and fractures.

[0108] Next, for the vibration item, the vibration frequency was 10 ⇔ 2000 Hz, the vibration acceleration was 5G, the sweep time was 20 minutes per reciprocation (sweep), and the test time was 4 hours for each of the x / y / z three axes, for a total of 12 hours of testing. The test results are as shown in Table 10 below.

Table 10

[0109] As shown in Table 10, the experimental results showed that the magnetic permeability decrease was 1.0 - 2.7%, the increase in core loss (@100 °C) was at most 0.9%, and the results met the AEC-Q200 Pass conditions without cracks and fractures.

[0110] On the other hand, for the strength item, a test was conducted using a UTM LS1 equipped with a maximum load application of 1 kN to apply a load vertically downward along the height direction of the toroidal core (i.e., Direction: Compression). Here, the application acceleration was 30 mm / min and the limit load was 1000 N. Also, the specifications of the magnetic cores used in the test are as shown in Table 11 below.

Table 11

[0111] The test results of the strength item for cores under the conditions as shown in Table 11 are as shown in Table 12 below.

Table 12

[0112] Referring to Table 12, the load at which breakage occurred in a total of 5 experiments was 670 - 960 N, and the average value was 824 N. The original data (raw data) of the experimental results corresponding to 4 of these are shown in Figure 8.

[0113] The excellent performance of the magnetic core according to the embodiments described so far, namely thermal shock, shock resistance, vibration and strength, is due to the component distribution at grain boundaries caused by adding constituent materials after the raw materials, unlike the raw materials. This will be described with reference to FIGS. 9a to 9c.

[0114] FIG. 9a shows the component distribution of cobalt and nickel in the magnetic core according to one embodiment, and FIG. 9b shows the component distribution of cobalt and nickel in the magnetic core according to the comparative example. FIG. 9c shows the component distribution of other non-magnetic additives according to one embodiment.

[0115] Each graph shown in FIGS. 9a to 9c shows the distribution of each composition material along the particles and the grain boundaries adjacent to them based on a scanning electron microscope (SEM) and an energy dispersive X-ray spectroscopy (EDS). Also, in the comparative example, the composition ratio of the constituent materials is the same as that of the magnetic core according to one embodiment, but all the composition materials are added together from the first mixing without post-addition.

[0116] First, referring to FIGS. 9a and 9b, in the magnetic core according to the embodiment, since cobalt and nickel are present at 40% or more (i.e., 0.4 wt%) with respect to the maximum distribution (i.e., 1 wt%) in the particle region even at the grain boundaries, the content ratio of Co and Ni at the grain boundaries to the particles becomes 0.4 or more. However, it can be seen that in the magnetic core according to the comparative example, the contents of cobalt and nickel at the grain boundaries drop to 0.3 wt%. More specifically, when comparing the content minimum point 910 of the magnetic additive at the grain boundaries of the embodiment with the content minimum point 920 of the magnetic additive at the grain boundaries of the comparative example, it is considered that about 0.04 wt% to 0.08 wt%, that is, about 4% to 8% of the magnetic additives (Co, Ni) are more distributed.

[0117] Ultimately, in the magnetic core according to the embodiment, a significant amount of cobalt and nickel, even 0.4 wt% or more, is distributed at the grain boundaries, resulting in excellent thermal shock and low-temperature characteristics. On the other hand, as shown in FIG. 9c, it can be seen that non-magnetic additives, namely components such as Si, Ca, Ta, Zr, and V, mainly exist within the grain boundaries. Specifically, in the direction where the distance increases from 0 (i.e., the direction of adjacent particles), the content of the non-magnetic additive in the particle region gradually increases. If the area corresponding to the content of the non-magnetic additive in the relevant region is taken as 1, the area corresponding to the content of the non-magnetic additive at the grain boundary is 9 - 10. Therefore, the ratio of the sum of the contents of the non-magnetic additive at the grain boundary located between at least one crystal grain (particle) and one crystal grain (particle) adjacent to it in a specific direction is 0.1 or more. Such main compositions and additive contents can be measured using a wavelength dispersive X-ray fluorescence (WDXRF) instrument.

[0118] The description of each of the above-described embodiments can be applied to other embodiments as long as the contents do not contradict each other.

[0119] The present invention has been described based on the embodiments above, but this is merely illustrative and does not limit the present invention. Those with ordinary knowledge in the field to which the present invention pertains will understand that various modifications and applications not exemplified above are possible within the scope not departing from the essential characteristics of this embodiment. For example, each component specifically shown in the embodiment can be implemented with modifications. And the differences related to such modifications and applications should be construed as being included in the scope of the present invention defined by the appended claims.

Claims

1. A main composition material containing manganese (Mn) oxide in a molar ratio of 37 to 44 mol%, zinc (Zn) oxide in a molar ratio of 9 to 16, iron (Fe) oxide in a molar ratio of 42 to 52, cobalt (Co) oxide in a molar ratio of 0.1 to 1 of the magnetic additive component, nickel (Ni) oxide in a molar ratio of 0.1 to 0.5 of the magnetic additive component, and a magnetic compound containing a non-magnetic additive, wherein the magnetic compound includes a plurality of crystal grains (grain) and a grain boundary (grain boundary) corresponding to the boundary between the plurality of crystal grains (grain), a magnetic core in which the cobalt content and the nickel content in the central region of the grain boundary are each 40% or more of the cobalt content and the nickel content in the central region of the pre-crystal grain.

2. The magnetic core according to claim 1, wherein the non-magnetic additive includes four or more of silicon (Si) oxide, calcium (Ca) oxide, tantalum (Ta) oxide, vanadium (V) oxide, niobium (Nb) oxide, and zirconium (Zr) oxide.

3. The silicon oxide is 50 to 200 ppm, the calcium oxide is 200 to 700 ppm, the tantalum oxide is 200 to 900 ppm, the vanadium oxide is 50 to 500 ppm, and the zirconium oxide has a content of 50 to 500 ppm, respectively, for the magnetic core according to claim 2.

4. A main composition material containing manganese (Mn) oxide in a molar ratio of 37 to 44, zinc (Zn) oxide in a molar ratio of 9 to 16, iron (Fe) oxide in a molar ratio of 42 to 52, cobalt (Co) oxide in a molar ratio of 0.1 to 1 of the magnetic additive component, nickel (Ni) oxide in a molar ratio of 0.1 to 0.5 of the magnetic additive component, and a magnetic compound containing a non-magnetic additive, wherein the non-magnetic additive includes 50 to 200 ppm of silicon oxide, 200 to 700 ppm of calcium oxide, 200 to 900 ppm of tantalum oxide, 50 to 500 ppm of zirconium oxide, and 50 to 500 ppm of vanadium oxide, wherein the magnetic compound includes a plurality of crystal grains (grain) and a grain boundary (grain boundary) corresponding to the boundary between the plurality of crystal grains (grain), a magnetic core in which the ratio of the content of at least one of the non-magnetic additives in the crystal grains to the content of the at least one of the non-magnetic additives in the grain boundary is 1:9 to 1:10.

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