JP5305126B2 - Soft magnetic powder, method of manufacturing a dust core, dust core, and magnetic component - Google Patents

Description

The present invention relates to a dust core having a high magnetic flux density and a low loss, which is used in various reactors, noise countermeasures, various motors, various generators, and the like, and a magnetic component using the same.

  For powder magnetic cores used in various reactors, noise countermeasures, various motors, various generators, etc. and soft magnetic powders that produce them, iron powder, silicon steel, Fe-Si-Al alloys, amorphous alloys and nanocrystalline alloy materials Etc. are used.

  For magnetic core materials such as various reactors, noise countermeasures, various motors, various generators, etc., soft magnetic materials with high magnetic flux density and low loss have been demanded. It is getting complicated. Attention has been focused on powder magnetic cores that use soft magnetic powder materials that enable three-dimensional design with a higher degree of freedom from materials that have only two-dimensional freedom, such as conventional silicon steel sheets and amorphous ribbons. ing. Further, the dust core made of soft magnetic powder has a feature that eddy current loss can be reduced by appropriately performing insulation treatment between powders or flattening the shape of the powder.

A dust core is generally manufactured in the following procedure. By applying mechanical pulverization or atomization to a soft magnetic alloy having a predetermined composition, a soft magnetic powder is obtained. In order to insulate the soft magnetic powder, for example, an insulating material such as water glass, silicone phosphate resin, phenol resin, epoxy resin, polyimide resin and the like having a binding ability are mixed to form an insulating layer on the powder surface. To produce a soft magnetic powder coated with an insulating film. For the formation of the insulating layer, for example, a method of insulating by mixing a ceramic powder having a very small particle size such as silica or alumina powder and allowing it to be present in the gaps between the soft magnetic powders when compacted, or TEOS For example, a method of forming an insulating layer by attaching a metal alkoxide or the like to the powder surface and performing a heat treatment is performed.
The dust core is manufactured in a predetermined shape by filling a soft magnetic powder with an insulating coating into a mold together with a lubricant such as zinc stearate and press-molding it. Moreover, although the molding distortion at the time of press molding is introduced into the powder, the molding distortion is removed by annealing at a predetermined temperature to improve the performance.

  When such a dust core is used in the above-described applications, it is important that the core loss during use is small and the magnetic flux density of the core is high. If the magnetic core loss is reduced, the loss of power energy is reduced, resulting in higher efficiency and energy saving. In addition, if the magnetic flux density is increased, the DC superposition characteristics and the like can be improved, and the powder magnetic core can be downsized. Not only can the product be downsized, but also the parts around the powder magnetic core can be downsized. It is also expected that design flexibility will be improved by reducing material costs and saving circuit space.

  The core loss is usually separated into hysteresis loss and eddy current loss. The hysteresis loss is affected by the metal magnetic powder composition and structure, or the distortion of the metal magnetic powder generated during press molding. Eddy current loss is affected by the size of metal magnetic powder particles and the insulation between metal powder particles. Hysteresis loss is correlated with coercivity. In order to obtain a dust core having a low magnetic core loss, a soft magnetic powder having a low coercive force is required.

  The most used soft magnetic powder for dust cores is iron powder. However, if you want to obtain a dust core with lower loss, especially low hysteresis loss, the coercive force is smaller than iron. Silicon steel powder is used, and in order to further reduce hysteresis loss, Fe-Si-Al alloy, amorphous alloy, and nanocrystalline alloy powders are used. In order to obtain an amorphous alloy or nanocrystalline alloy powder, for example, a method of mechanically pulverizing a quenched ribbon, a method of directly obtaining a powder by atomization, or the like is applied.

  When the quenched ribbon is obtained by mechanical pulverization, first, for example, the quenched ribbon is produced by a single roll method or a twin roll method, and then a pulverizer such as a disk mill, a ball mill, or a pin mill is used. To obtain a powder. However, a quenched ribbon that provides good magnetic properties is generally difficult to pulverize and needs to be subjected to an embrittlement heat treatment before pulverization, and because pulverization distortion is introduced into the powder by pulverization. Good magnetic properties in the band may not be reflected in the powder.

  When an amorphous alloy or nanocrystalline alloy powder is manufactured by atomization, the composition is generally limited by the rapid cooling rate of the atomization apparatus, and the magnetic characteristics are affected. For example, in the case of a conventional Fe-based nanocrystalline alloy, since it contains an element that lowers the saturation magnetic flux density such as Nb, there is a problem that the saturation magnetic flux density is lowered and a dust core with a high magnetic flux density cannot be obtained.

  In Non-Patent Document 1, it is said that the cooling mechanism of the atomizing apparatus is improved to increase the rapid cooling rate, and amorphous powder having a composition that cannot be obtained by conventional atomization can be produced. Non-Patent Document 2 uses the amorphous powder to obtain a low-loss dust core.

  However, although the powder magnetic core manufactured using the Fe-based amorphous soft magnetic powder and the conventional Fe-based nanocrystalline soft magnetic powder shows low loss, the saturation flux density of the material itself is 1.68 T or less, Fe powder, silicon Saturation magnetic flux density is lower than steel powder. The magnetic flux density of the dust core is obtained by multiplying the saturation magnetic flux density of the material by the space factor. Fe-based amorphous soft magnetic powder is hard and has poor moldability compared to crystalline materials such as Fe powder and silicon steel powder, so the space factor of the dust core is as high as that of crystalline materials such as Permalloy and Fe. However, it is difficult to increase the magnetic flux density of the dust core.

KUBITA TECHNICAL REPORT No.29 7-13 IEEJ Magnetics Study Group Material MAG-98, 201-215, pages 73-78

An object of the present invention is to obtain a dust core having a low loss and a high magnetic flux density equivalent to or less than a dust core using an Fe-based amorphous powder . It is another object of the present invention to provide a heat treatment process that can efficiently and stably reduce core loss when a dust core is formed .

The present invention has an average particle size of 300 μm or less and a composition formula: Fe _100-xy A _x X _y (where A is at least one element selected from Cu and Au, X is B, Si, S , C, P, Al, Ge, Ga, and Be), and a soft magnetic powder represented by 0 <x ≦ 5 and 10 ≦ y ≦ 24 in atomic% is used. A dust core,
The soft magnetic powder has a matrix structure in which crystal grains having a crystal grain size of 2 nm or more and 60 nm or less are dispersed in an amorphous material at a volume fraction of 30% or more, and a crystal layer composed of the crystal structure is formed on the outermost surface. And having an amorphous layer between the crystal layer and the matrix structure,
A dust core, wherein the soft magnetic powder has a space factor of 70.0% or more.

Soft magnetic powder used in the present invention, between the amorphous layer and the matrix structure, or may have a coarse crystal grain layer composed of the particle diameter than the average grain size of the matrix structure is large crystals.

The soft magnetic powder used in the present invention may have a flat shape, and preferably has a thickness of 10 μm or less and an aspect ratio of 30 or more. When flat powder having a large aspect ratio is used, eddy current loss of the dust core can be reduced.

Soft magnetic powder used in the present invention, by spraying the molten metal, may be one produced by using a two-stage quench process of quenching thereafter brought immediately into contact with the cooling medium. Alternatively , it may be produced by pulverizing a quenched ribbon or flake produced by a single roll method, a twin roll method or a strip casting method.

The production method, the soft magnetic powder has a grain size of 60nm or less (not including 0) crystal grains dispersed matrix structure with a volume fraction of 30% or more in the amorphous, the outermost surface An average temperature increase rate of 300 ° C. or higher is 100 ° C./min or higher and a maximum temperature T is soft magnetic so that a crystal layer composed of a crystal structure is formed and an amorphous layer is provided between the crystal layer and the matrix structure. Heat treatment is preferably performed at a crystallization temperature of the powder −30 ° C. ≦ T ≦ crystallization temperature + 50 ° C. It is possible to produce a dust core having a low magnetic loss and a high magnetic flux density, which has excellent soft magnetic properties.

  The heat treatment is preferably performed so that an average temperature rising rate of 300 ° C. or higher is 100 ° C./min or higher, and more preferably, an average temperature rising rate of 300 ° C. or higher is 150 ° C./min or higher.

  In the heat treatment, the maximum temperature T is preferably a crystallization temperature of −30 ° C. ≦ T ≦ crystallization temperature + 50 ° C., more preferably −10 ° C. ≦ T ≦ crystallization temperature + 30 ° C. preferable. For example, in the soft magnetic powder A having a crystallization temperature of 430 ° C., the maximum temperature TA is preferably 400 ° C. ≦ TA ≦ 480 ° C., and more preferably 420 ° C. ≦ TA ≦ 460 ° C.

  The heat treatment is performed in a heat treatment pattern in which a temperature cycle of cooling to 300 ° C. or lower is repeated a plurality of times after raising the temperature to the maximum temperature, thereby stably producing a dust core having a low loss and a high magnetic flux density that excels in soft magnetic properties. Can be made. As a method of repeating the cycle, for example, one cycle may be performed in a box furnace or the like, and the process may be performed in several times. For example, a continuous furnace or the like may be performed continuously in several cycles as one process. It may be done.

By making the powder magnetic core using the manufacturing method of the present invention, it is possible to obtain 0.1 T, core loss of 10kHz is excellent dust core following soft magnetic characteristics 5.0 W / kg.

By using the dust core of the present invention, it is possible to obtain a high-performance magnetic parts.

  The soft magnetic powder of the present invention has an average particle size of 300 μm or less and a crystal structure having crystal grains of 60 nm or less (excluding 0) dispersed in an amorphous material by 30% or more by volume fraction. And having an amorphous layer on the surface side of the powder. Since the soft magnetic powder of the present invention has a structure different from that of the parent phase inside, the soft magnetic powder having a high saturation magnetic flux density and a low coercive force which cannot be obtained by conventional amorphous powder and nanocrystal powder. It was found that can be realized.

  As shown in FIGS. 2A and 2B, the soft magnetic powder of the present invention has a crystal grain size of 60 nm or less (excluding 0) at a position 120 nm deep from the surface 2 of the powder. It has a matrix structure D in which a volume fraction of 30% or more is dispersed in the crystal and has an amorphous layer B on the surface side of the powder. This amorphous layer may be observed over the entire periphery of the powder, or only a part of the soft magnetic powder pulverized from the ribbon shape may be observed. Some of the soft magnetic powders have a crystal layer A formed of a crystal structure on the outermost surface and the amorphous layer B formed on the inner side of the crystal layer A. Further, a coarse crystal grain layer C made of crystals having a grain size larger than the average grain size of the matrix structure may be provided between the amorphous layer B and the matrix structure D.

  The reason why the amorphous layer appears is estimated below. This alloy system has Fe as a main component and Cu and / or Au (hereinafter referred to as element A) is essential. The element A, which is almost non-solid solution with Fe, aggregates to form nano-order clusters and assists in the nucleation of crystal grains. In the portion away from the surface, the A element is easily dispersed uniformly, and therefore a nanocrystalline matrix structure D is formed. In addition, due to the non-solid solution property, the A element tends to segregate on the outermost surface, and the concentration of the A element becomes high, and a crystal structure is formed in the same manner as the parent phase. On the other hand, in the interior immediately below the outermost surface, the concentration of the A element is lowered by the amount of the A element taken on the surface side. Therefore, in this region, nucleation of crystal grains does not occur and an amorphous layer is formed. In the soft magnetic powder of the present invention, a fine crystal grain layer is deposited by heat treatment, and the concentration of microcrystal grain nuclei is determined by the distribution of element A as described above. For this reason, nuclei are unlikely to appear near the surface, and an amorphous layer appears to be formed.

Further, the reason why the coarse crystal grain layer C appears is estimated as follows. Further inside the amorphous layer, the concentration of the A element is not as high as that of the region that forms the matrix structure, and nucleation is also low. The grain size of nanocrystal grains is determined by the balance between the concentration of nuclei and the speed of grain growth. In the region of the matrix structure in which the concentration of the A element is uniform, the difference in structure due to the difference in the heating rate does not appear easily. However, in the C region where the A element is low, if the heating rate is slow, it is sufficient for the thermal diffusion of the A element. Given the time, the number of nuclei decreases. Therefore, the crystal grains are easily coarsened, and the coarse crystal grain layer C is formed. For example, when the rate of temperature increase is increased, the crystal grains of the coarse crystal grain layer C become fine and the average grain size approaches the parent phase. Further, the width of the coarse crystal grain layer C decreases. By controlling the rate of temperature rise, the structure is controlled and magnetic properties suitable for the application can be obtained.
Here, the coarse crystal grain layer C refers to a portion that is 1.5 times or more the average crystal grain size of the matrix structure. Moreover, it is preferable that the average crystal grain size of the coarse crystal grain layer C is not more than twice the average crystal grain size of the parent phase structure.

The crystal grain size is measured by taking an average value of the major axis and the minor axis of the structure observed in the structure photograph taken with an electron microscope. The average particle size is an average value of 30 or more crystal grain sizes.
The volume fraction of crystal grains is determined by the line segment method, that is, assuming an arbitrary straight line in the microstructure, the length of the test line is Lt, the length Lc of the line occupied by the crystal phase is measured, and is occupied by the crystal grains. It is _calculated | required by _calculating | requiring the ratio of the length of the line _LL = _Lc / _Lt * 100. Here, the volume fraction of crystal grains is V _V = L _L.

With the dust core of the present invention, a dust core having a saturation magnetic flux density of 1.4 T or more can be obtained. When the soft magnetic powder used in the present invention is measured by VSM, the saturation magnetic flux density of the powder is 1.80 T or more, and the space factor of the soft magnetic powder in the dust core is 70.0% or more. In addition, the dust core using the soft magnetic powder of the present invention has a large aspect ratio and can reduce eddy current loss compared to a dust core using a spherical amorphous powder.

The crystal grains in the matrix structure preferably have a volume fraction of 50% or more, more preferably 60% or more. Although the average crystal flow diameter needs to be 60 nm or less, the particularly desirable average crystal grain diameter is 2 nm to 25 nm, and particularly low coercive force and magnetic core loss are obtained in this range.
The fine crystal grains formed in the above-described alloy of the present invention have a body-centered cubic (bcc) crystal phase mainly composed of Fe, and Si, B, Al, Ge, etc. may be dissolved therein. Further, a regular lattice may be included. The balance other than the crystalline phase is mainly an amorphous phase, but an alloy consisting essentially of the crystalline phase is also included in the present invention. There may be a face-centered cubic phase (fcc phase) partially containing Cu.
Further, when an amorphous phase is present around the crystal grains, the resistivity is increased, the crystal grains are refined by suppressing the crystal grain growth, and more preferable soft magnetic characteristics can be obtained.
The soft magnetic powder of the present invention shows lower magnetic core loss when no compound phase is present, but the compound phase may be partially included.

The soft magnetic powder of the present invention has a composition formula: Fe _100-xy A _x X _y (where A is at least one element X selected from Cu and Au is B, Si, S, C, P, And at least one element selected from Al, Ge, Ga, and Be) and those represented by 0% x≤5 and 10≤y≤24 in atomic% are preferable. The reason for limitation will be described below.

The amount of element A (Cu, Au) is 5% or less (excluding 0%). The element A in the alloy composition of the present invention is particularly important. As described above, since the A element is almost non-solid solution with Fe, it diffuses by heat treatment. In particular, when heat treatment is performed that tends to cause temperature distribution or temperature difference between the powder surface and the inside, there are sites where diffusion is likely to occur and sites where mutual diffusion is likely to be hindered, and the internal structure is inclined and layered. It changes to. In order to control the magnetic properties, it is effective to control the size of the powder, the composition, the heat treatment temperature during heat treatment, the heat treatment time, the temperature raising rate, and the temperature lowering rate.
The amount of element A is preferably 3% or less. In order to obtain the above effect, the element A is preferably added in an amount of 0.1 atomic% or more, further 0.5 atomic% or more, and further 0.8 atomic% or more. In consideration of the raw material cost, it is preferable to select Cu as the element A.

X element (B, Si, S, C, P, Al, Ge, Ga, Be) is an element indispensable for forming the soft magnetic powder of the present invention in which A element (Cu, Au) is present in the same powder. It is. If it is less than 10 atomic%, the effect of promoting the formation of amorphous is insufficient. On the other hand, if it exceeds 24 atomic%, the soft magnetic characteristics are deteriorated. A preferable range is 12 atom% or more and 20 atom% or less.
In particular, B is an important element for promoting the formation of amorphous and is preferably added. When the concentration of B is 10 ≦ y ≦ 20 atomic%, an amorphous phase can be stably obtained while maintaining a high Fe content.
Further, when Si, S, C, P, Al, Ge, Ga, and Be are added, the temperature at which Fe—B having a large magnetocrystalline anisotropy starts to precipitate increases, so that the heat treatment temperature can be increased. By applying a high-temperature heat treatment, the proportion of the microcrystalline phase increases and B _S increases. In addition, there is an effect of suppressing deterioration and discoloration of the sample surface. The addition amount of Si, S, C, P, Al, Ge, Ga, and Be is preferably more than 0 atomic% to 7 atomic%. Particularly, Si is preferable since this effect is remarkable.

  A part of Fe may be substituted with at least one element selected from Ni and Co that are dissolved in Fe and A elements together. Soft magnetic powders substituted with these elements have a high ability to form an amorphous phase and can increase the content of element A. Increasing the content of element A promotes refinement of the crystal structure and improves soft magnetic properties. In addition, when Ni and Co are replaced, the saturation magnetic flux density increases. Substituting a large amount of these elements leads to an increase in the price. Therefore, the amount of substitution of Ni is less than 10%, preferably less than 5%, more preferably less than 2%. In the case of Co, less than 10%, preferably Less than 2%, more preferably less than 1% is suitable.

Part of Fe is Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, platinum group elements, Ag, Zn, In, Sn, As, Sb, Sb, Bi, Y, N When substituted with at least one element selected from O, O, and rare earth elements, these elements preferentially enter the amorphous phase that remains after heat treatment together with the A element and metalloid element, so that fine grains with high Fe concentration Helps to generate Therefore, it contributes to the improvement of soft magnetic characteristics. On the other hand, since the substantial magnetic player in the alloy of the present invention is Fe, it is necessary to keep the Fe content high. However, the inclusion of these elements having a large atomic weight means the Fe content per unit weight. Will drop. In particular, when the element to be substituted is Nb or Zr, the substitution amount is less than about 5%, more preferably less than 2%. When the element to be substituted is Ta or Hf, the substitution amount is less than 2.5%, More preferably, it is less than 1.2%. Further, when Mn is replaced, the saturation magnetic flux density is lowered, so that the replacement amount is appropriately less than 5%, more preferably less than 2%.
However, in order to obtain a particularly high saturation magnetic flux density, the total amount of these elements is preferably 1.8 atomic% or less. Moreover, it is more preferable that the total amount is 1.0 atomic% or less.

  A specific production method of the present invention is a method in which quenching is performed at a cooling rate of 100 ° C./sec or more, and crystal grains having an average particle size of 30 nm or less are contained in the amorphous phase in a volume fraction of more than 0%. It is obtained by producing a Fe-based alloy having a structure dispersed at less than 30%, and then processing this and performing a heat treatment in the vicinity of the crystallization temperature to form a microcrystalline structure having an average grain size of 60 nm or less.

In the present invention, as a method of rapidly cooling the molten metal, in addition to the single roll method, a twin roll method, a rotating liquid prevention method, a gas atomizing method, a water atomizing method, gas or water spraying the molten metal, immediately after water or There is a two-stage quenching method in which two-stage cooling is performed continuously by bringing it into contact with a cooling medium such as a water-cooled disk or a water-cooled roll, and flakes, ribbons, and powders can be produced. Further, it is desirable that the molten metal temperature at the time of rapid cooling of the molten metal is higher by about 50 ° C. to 300 ° C. than the melting point of the alloy.
The ultra-quenching method such as the single roll method or the two-stage quenching method using a cooling roll can be carried out in the atmosphere or in an atmosphere such as local Ar or nitrogen gas if it does not contain an active metal. In the case of containing a metal, the gas atmosphere in the vicinity of the roll surface at the nozzle tip is controlled in an inert gas such as Ar or He, in nitrogen gas or under reduced pressure. Also, alloy powder is produced while CO ₂ gas is blown onto the roll and CO gas is burned near the roll surface near the nozzle.
The cooling roll peripheral speed is preferably in the range of 30-50 m / s in the single roll method, and in the range of 10-50 m / s in the two-stage quenching method using the cooling roll, and the cooling roll material is pure copper or Cu- Copper alloys such as Be, Cu—Cr, Cu—Zr, and Cu—Zr—Cr are suitable. When manufacturing in large quantities, it is preferable that the cooling roll has a water cooling structure.

Generally, the soft magnetic powder of the present invention is provided by rapid cooling at a cooling rate (10 ⁵ ° C / sec) or more necessary for forming an Fe-based amorphous alloy or nanocrystalline alloy. As a rapid cooling method having a cooling rate of 10 ⁵ ° C / sec or more, a single roll method, a water atomizing method, a method of spraying a powder onto a cooling medium such as water or oil with a gas and then settling, There are methods such as spraying powder onto a water-cooled disk rotated at a rapid cooling.

  As a method for producing a powder having a non-parallel phase by rapid cooling directly from the molten metal, a method in which the molten metal is sprayed with a high-pressure gas or the like and further brought into contact with a cooling medium such as a rotated water-cooled disk is preferably used. In the present invention, this is called a two-stage quenching method (hereinafter abbreviated as two-stage quenching). In the two-stage rapid cooling, the process of spraying the molten metal with high-pressure gas and the process of rapidly cooling the molten metal particles in close contact with the water-cooled disk are performed. The pre-process is also a process of cooling while dividing the molten metal, and the particle size distribution of the powder to be produced can be controlled by changing the pressure of the high-pressure gas and the setting of the spray port for ejecting the gas. The post-process is a process of rapidly cooling the molten metal particles divided in the pre-process, and the rapid cooling structure can be controlled by the number of rotations of the water-cooled disk and surface adhesion.

  As the high-pressure gas, any inert gas (for example, nitrogen, argon, helium) can be used. Moreover, although the temperature of gas is not prescribed | regulated, since a desired rapid cooling structure | tissue will not be obtained if the molten metal is cooled before spraying and contacting a water-cooled disk, it is desirable that it is not too low temperature. In the present invention described later, it is used at room temperature.

  The shape of the water-cooled disk may be a tray shape in which the surface on which the molten metal is sprayed and sprayed is perpendicular to the spraying direction, or a conical shape having an angle with the spraying direction. In the case of a tray, a thin disc-shaped powder is formed. In the case of a cone, a thin powder having an elliptical shape is formed. In this way, the shape of the powder can be controlled by changing the shape of the water-cooled disk.

  The thickness of the powder produced by the two-stage quenching is about 1 to 10 μm, and the thickness is less than half that of the amorphous ribbon produced by the single-roll method. Therefore, the two-stage quenching is more efficient than the single-roll method. And a uniform non-parallel texture is obtained.

  As a method for obtaining the soft magnetic powder, it is also possible to obtain by pulverizing a quenched ribbon or flakes produced by a single roll method, a twin roll method or a strip casting method. As a method for pulverizing the ribbon, general pulverization equipment such as a disk mill, a ball mill, or a pin mill can be used. The pulverization step may be performed before or after the heat treatment described later. Moreover, you may perform separately the heat processing for removing the grinding | pulverization distortion introduce | transduced into a powder by a grinding | pulverization process.

  When the soft magnetic powder of the present invention is subjected to a treatment such as forming an insulating layer on the surface by a chemical conversion treatment for coating the surface of the alloy powder, forming an oxide insulating layer on the surface by an anodic oxidation treatment, and insulating between powders. More favorable results are obtained. The insulating layer may be an organic or inorganic binder, or may be formed by oxidizing or nitriding the powder surface by heat treatment in an oxygen atmosphere or nitrogen atmosphere. This is particularly because the effect of eddy currents at high frequencies across the powder is reduced and magnetic core loss at high frequencies is improved.

  When the soft magnetic microcrystalline powder of the present invention is formed into a powder magnetic core, it may be any of cold forming, warm forming, isostatic pressing, plasma sintering forming, magnetic field forming, and the like. In particular, when plasma sintering is performed, the effect of increasing the space factor and the effect of reducing the loss are remarkably obtained. In addition, when molding is performed in a magnetic field, it is possible to align the flat powder arrangement, and the effect of high magnetic permeability and loss reduction can be obtained.

  The soft magnetic powder of the present invention realizes excellent soft magnetic properties by performing a heat treatment such that an average temperature rising rate of 300 ° C. or higher is 100 ° C./min or higher. In the case of performing this heat treatment, Fe having a structure in which crystal grains having an average particle size of 30 nm or less are dispersed in the amorphous phase with a volume fraction of more than 0% and less than 30% in the amorphous phase obtained by the rapid cooling described above. It is preferable that the base soft magnetic powder is formed into a green compact.

  In the case where the heat treatment is performed as a green compact, a microcrystalline structure is formed by the heat treatment, and at the same time, molding distortion introduced into the powder during molding is removed. In order to produce microcrystals from the amorphous phase, the structure structure changes, and the structure change plays an effective role in removing molding strain. When molding distortion remains in the green compact, the coercive force increases according to the degree of residual, and the loss increases. The removal of molding distortion is the most important issue in the method of manufacturing a dust core.

  In the heat treatment in which the average temperature rise rate of 300 ° C. or higher is 100 ° C./min or higher, the temperature rise rate is relatively fast. Therefore, depending on the structure of the heat treatment furnace and the program setting, the furnace set temperature and the actual sample temperature There may be a difference between In the powder magnetic core of the present invention, it is preferable that the crystallization temperature of the powder is a set temperature of the furnace, and the actual temperature of the sample is “crystallization temperature−30 ° C. ≦ T ≦ crystallization temperature + 50 ° C.”. More preferably, the actual temperature of the sample is “crystallization temperature−10 ° C. ≦ T ≦ crystallization temperature + 30 ° C.”.

  In the heat treatment of the green compact obtained by molding the soft magnetic powder of the present invention and having a crystallization temperature of 460 ° C., as shown in FIG. .Low loss of 10 W / kg or less can be realized under the conditions of 1T and 10 kHz. Furthermore, the low loss of 5 W / kg or less is realizable by making the maximum temperature of a sample into 450-490 degreeC.

  When the actual temperature of the sample is lower than “crystallization temperature −30 ° C.”, microcrystallization is not promoted, and not only the soft magnetic powder structure of the present invention is obtained, but also the molding strain cannot be completely removed. The core loss cannot be reduced sufficiently. When the actual temperature of the sample is higher than “crystallization temperature + 50 ° C.”, the crystal becomes coarse and the soft magnetic powder structure of the present invention cannot be obtained, so that the magnetic core loss cannot be sufficiently reduced.

  The heat treatment can produce a dust core having excellent soft magnetic characteristics even in one cycle, but can be stably produced by repeating several cycles. Since the above heat treatment has a relatively high rate of temperature increase, depending on the size and shape of the sample, there may be a temperature difference depending on the portion such as the vicinity of the surface of the sample and the inside of the sample. By repeatedly performing the heat treatment, uniform heat is applied to the entire powder, and the soft magnetic powder of the present invention with low magnetic core loss is obtained.

  As in the sample shown in FIG. 4, the magnetic core loss of 28 W / kg in one cycle could be reduced to 5 W / kg or less by repeating the heat treatment for two cycles or more. This is because in the first cycle, uniform microcrystallization cannot be performed over the entire sample, and an amorphous phase partially remains. By repeating the heat treatment for two cycles or more, microcrystallization is promoted and the magnetic core loss is reduced.

  According to the heat treatment method of the present invention, as shown in FIG. 4, the core loss at the 3rd to 4th cycles hardly changes, and within the scope of the present invention, the portion crystallized by increasing the number of cycles. The structure of the core does not become coarse, and the core loss does not deteriorate. At the mass production site, when heat-treating a large amount of samples at once, it is difficult to perform uniform heat treatment on all samples due to the effects of temperature distribution in the furnace and the difference in weight between samples. According to this heat treatment method, a dust core having stable and excellent soft magnetic properties can be produced by repeating the heat treatment cycle several times as necessary.

  According to the present invention, various types of reactors for large currents, choke coils for active filters, smooth choke coils, electromagnetic shielding materials and other noise countermeasure parts, motors, generators, etc., high saturation magnetic flux density and low coercive force. Since the soft magnetic powder and the powder magnetic core with high magnetic flux density and low loss using the same can be realized, the effect is remarkable.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
Example 1
In the single roll method, molten alloy heated to 1360 ° C is sprayed onto a water-cooled Cu roll rotating at a peripheral speed of 30 m / s to produce a 18 to 20 μm thick Fe _bal Cu _1.5 Si ₅ B ₁₃ alloy ribbon. did. The alloy ribbon was embrittled at a predetermined temperature and then pulverized to produce a flat powder having a thickness of 18 to 20 μm and a particle size of 300 μm or less. As a result of cross-sectional observation by X-ray diffraction and transmission electron microscope (TEM), it was confirmed that the structure was a structure in which fine crystals were dispersed in an amorphous phase by a volume fraction of less than 30%.
The prepared powder was subjected to TEOS treatment to uniformly form a SiO2 film having a thickness of 0.1 to 0.2 [mu] m on the powder surface to obtain an insulating coated soft magnetic flat powder. Furthermore, Zn-St powder as a lubricant was mixed, filled in a mold, and press-molded at a pressure of 10 to ²⁰ ton / cm ² .
The obtained molded body was heat-treated under conditions such that the average temperature rising rate of 300 ° C. or higher was 300 ° C./min or higher to obtain a dust core made of soft magnetic powder having a nanocrystal structure. Applying heat treatment after compacting is effective to completely remove the strain applied to the powder during molding. Table 1 shows the core loss Pcm at 0.1 T and 10 kHz, the saturation magnetic flux density Bs of the powder, and the space factor of the dust core. The apparent magnetic flux density of the powder magnetic core is the saturation magnetic flux density of the powder × the space factor. The dust core produced using the soft magnetic powder of the present invention has excellent magnetic properties such as having a core loss comparable to that of an amorphous dust core and having a magnetic flux density similar to that of a silicon steel powder dust core. .

(Example 2)
In a two-stage quenching method, molten alloy heated to 1400 ° C is sprayed with 6.0 MPa of nitrogen gas, and immediately after that, a cone with an outer diameter of 380 mm rotating at a peripheral speed of 10 m / s, a rotating shaft and a 45 ° inclined surface Molten metal was sprayed onto a Cu-Cr alloy water-cooled conical rotor of a shape to produce a flat powder of Fe _bal Cu _1.5 Si ₄ B ₁₄ alloy having a thickness of 1 to 5 μm. The flat powder has an aspect ratio of 30 or more and has an elliptical shape. Although an ellipse with a major axis of 500 μm or more can be obtained, only powder having a major axis of 300 μm or less was adopted in consideration of moldability. As a result of cross-sectional observation by X-ray diffraction and transmission electron microscope (TEM), it was confirmed that the structure was a structure in which fine crystals were dispersed in an amorphous phase by less than 30% by volume fraction.
The prepared powder was subjected to TEOS treatment to uniformly form a SiO2 film having a thickness of 0.1 to 0.2 [mu] m on the powder surface to obtain an insulating coated soft magnetic flat powder. Furthermore, Zn-St powder as a lubricant was mixed, filled in a mold, and press-molded at a pressure of 10 to 20 ton / cm2.
The obtained molded body was heat-treated under the condition that the average temperature rising rate of 300 ° C. or higher was 100 ° C./min or higher to obtain a dust core. Table 1 shows the core loss Pcm at 0.1 T and 10 kHz, the saturation magnetic flux density Bs of the powder, and the space factor of the dust core.

Example 3
In the single roll method, molten alloy heated to 1360 ° C is sprayed onto a water-cooled Cu roll rotating at a peripheral speed of 30 m / s to produce a 19 to 21 µm thick Fe _bal Cu _1.5 Si ₅ B ₁₃ alloy ribbon did. The alloy ribbon was embrittled at a predetermined temperature and then pulverized to produce a flat powder having a thickness of 18 to 20 μm and a particle size of 300 μm or less. This alloy powder was heat-treated. The heat treatment pattern was such that the average heating rate of 300 ° C. or higher was 100 ° C./min or higher. The holding temperature for the heat treatment was 450 ° C. for 10 minutes, and then rapidly cooled to obtain the soft magnetic powder of the present invention.

Example 4
The soft magnetic powder of the present invention produced in Example 1 was subjected to TEOS treatment to form a SiO ² coating on the surface of the powder to obtain an insulating coated soft magnetic flat powder. This powder was mixed with Zn-St powder as a lubricant, filled in a mold, and press-molded at a pressure of ²⁰ ton / cm ² . Thereafter, strain annealing heat treatment was performed at 400 ° C. for 2 hours to obtain a dust core. Table 1 shows the core loss Pcm at 0.1 T and 10 kHz, the saturation magnetic flux density Bs of the powder, and the space factor of the dust core.

(Example 5)
In a two-stage quenching method, molten alloy heated to 1400 ° C is sprayed with 6.0 MPa of nitrogen gas, and immediately after that, a cone with an outer diameter of 380 mm rotating at a peripheral speed of 10 m / s, a rotating shaft and a 45 ° inclined surface Molten metal was sprayed onto a Cu-Cr alloy water-cooled conical rotor of a shape to produce a flat powder of Fe _bal Cu _1.5 Si ₄ B ₁₄ alloy having a thickness of 1 to 5 μm. The flat powder has an aspect ratio of 30 or more and has an elliptical shape. Although an ellipse with a major axis of 500 μm or more can be obtained, only powder having a major axis of 300 μm or less was adopted in consideration of moldability. As a result of cross-sectional observation by X-ray diffraction and transmission electron microscope (TEM), it was confirmed that the structure was a structure in which fine crystals were dispersed in an amorphous phase in a volume fraction of less than 30%.
This alloy powder was heat-treated. The heat treatment pattern was such that the average heating rate of 300 ° C. or higher was 100 ° C./min or higher. The holding temperature for the heat treatment was 450 ° C. for 10 minutes, and then rapidly cooled to obtain the soft magnetic powder of the present invention.
FIG. 1 is a photograph of the structure of the soft magnetic powder of the present invention in the vicinity of the powder surface by a transmission electron microscope. It consists of the structure of the surface layer A of nanocrystal grains, the amorphous layer B, and the parent phase D in order from the outermost surface. In the mother phase, fine crystal grains having an average grain size of about 25 nm were present at 80% or more.
The soft magnetic powder was subjected to TEOS treatment to form a SiO2 coating on the surface of the powder to obtain an insulating coated soft magnetic flat powder. This powder was mixed with Zn-St powder as a lubricant, filled in a mold, and press-molded at a pressure of 10 to 20 ton / cm2. Thereafter, strain annealing heat treatment was performed at 400 ° C. for 2 hours to obtain a dust core. Table 1 shows the core loss Pcm at 0.1 T and 10 kHz, the saturation magnetic flux density Bs of the powder, and the space factor of the dust core. Compared with Example 1-3 in Table 1, the magnetic core loss is slightly higher. This is presumably because the nanocrystals were coarsened by the annealing heat treatment after compaction because the nanocrystallization heat treatment was performed at the time of the powder.

(Example 6)
A dust core was produced in the same manner as in Example 1 except that the raw materials having the alloy compositions shown in Table 2 were used. Table 2 shows the magnetic core loss Pcm, the powder saturation magnetic flux density Bs, and the space factor of the dust core at 0.1 T and 10 kHz.

(Example 7)
In the single roll method, molten alloy heated to 1360 ° C is sprayed onto a water-cooled Cu roll rotating at a peripheral speed of 30 m / s to produce a 18 to 20 μm thick Fe _bal Cu _1.5 Si ₅ B ₁₃ alloy ribbon. did. The alloy ribbon was embrittled at a predetermined temperature and then pulverized to produce a flat powder having a thickness of 18 to 20 μm and a particle size of 300 μm or less.
The prepared powder was subjected to TEOS treatment to uniformly form a SiO2 film having a thickness of 0.1 to 0.2 [mu] m on the powder surface to obtain an insulating coated soft magnetic flat powder. Furthermore, Zn-St powder as a lubricant was mixed, filled in a mold, and press-molded at a pressure of 10 to 20 ton / cm2.
The obtained molded body was heated at an average temperature increase rate of 300 ° C. or higher at 300 ° C./min, heated to 430 ° C., and then immediately cooled to 300 ° C. or lower repeatedly 1 to 4 times. It was. As shown in FIG. 4, the core loss was reduced by repeating the heat treatment.

(Example 8)
The molded body produced in the same manner as in Example 7 was heated at an average temperature rising rate of 300 ° C. or higher at 300 ° C./min, and after reaching the maximum temperature of 400 to 583 ° C., immediately cooled rapidly to 300 ° C. or lower. A heat treatment was performed. In FIG. 3, the core loss varies depending on the maximum temperature reached, but the core loss decreased at 430 to 510 ° C.

  By composing compact magnetic parts from this high saturation magnetic flux density and low loss soft magnetic powder, various reactors for large currents such as anode reactors, choke coils for active filters, smooth choke coils, magnetic shields, electromagnetic shield materials High performance or small magnetic parts suitable for noise countermeasure parts such as motors, generators and the like can be realized.

The structure photograph which shows the layered structure seen near the surface of soft-magnetic powder. The schematic diagram which shows the state of the structure | tissue of the soft-magnetic ribbon of this invention. The figure which shows the relationship between the holding temperature of heat processing, and a magnetic core loss. The figure which shows the relationship between the cycle number of heat processing, and a magnetic core loss. Organization picture

Explanation of symbols

  1: soft magnetic powder, 2: powder surface

Claims (5)

The average particle size is 300 μm or less, and the composition formula is Fe _100-xy A _x X _y (where A is at least one element selected from Cu and Au, X is B, Si, S, C, P) , Al, Ge, Ga, and Be), and a powder magnetic core using soft magnetic powder represented by 0 <x ≦ 5 and 10 ≦ y ≦ 24 in atomic% Because
The soft magnetic powder has a matrix structure in which crystal grains having a crystal grain size of 2 nm or more and 60 nm or less are dispersed in an amorphous material at a volume fraction of 30% or more, and a crystal layer composed of the crystal structure is formed on the outermost surface. And having an amorphous layer between the crystal layer and the matrix structure,
A dust core, wherein the soft magnetic powder has a space factor of 70.0% or more.   2. The dust core according to claim 1, wherein the core loss at 0.1 T and 10 kHz is 5.0 W / kg or less.   The said soft magnetic powder has a coarse crystal grain layer which consists of a crystal | crystallization with a larger particle size than the average particle diameter of the said mother phase structure | tissue between the said amorphous layer and a mother phase structure | tissue. Item 3. The dust core according to Item 2.   4. The soft magnetic powder according to claim 1, wherein the soft magnetic powder is manufactured using a two-stage quenching method in which a molten metal is sprayed and then immediately brought into contact with a cooling medium and rapidly cooled. Powder magnetic core.   A magnetic component using the dust core according to any one of claims 1 to 4.