JP2016197720A - Magnetic core and manufacturing method therefor, and on-vehicle component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic core suitable for high frequency application, and to provide a manufacturing method therefor.SOLUTION: In a magnetic core including a layered body of an Fe-based nano crystal alloy ribbon, and a resin contained in the layered body, when heating test is performed by raising the temperature, in the atmosphere, from room temperature to 160°C in 20 minutes, and after holding that temperature for 500 hours, lowering the temperature to room temperature by air-cooling, the drop rate of impedance relative permeability μat frequency 100 kHz is less than 5%, before and after the heating test. A manufacturing method for magnetic core includes a step of making a layered body of an Fe-based nano crystal alloy ribbon, a first heat treatment step of precipitating a nano crystal, a second heat treatment step of holding the temperature less than the nano crystallization start temperature in an atmosphere of more oxidative than the atmosphere in the first heat treatment step, and a step of impregnating with resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic core formed from an Fe-based nanocrystalline alloy, a manufacturing method thereof, and a vehicle-mounted component.

  The Fe-based nanocrystalline alloy is a soft magnetic material having excellent soft magnetic characteristics that can achieve both a high saturation magnetic flux density and a high relative magnetic permeability, and is widely used as a material such as a magnetic core of a common mode choke coil. The common mode choke coil is connected to a switching power supply or the like and used as a noise filter for suppressing high frequency noise. The applicant of the present application has developed and manufactured Finemet (registered trademark) as an Fe-based nanocrystalline alloy suitable for such applications.

  As the composition of the Fe-based nanocrystalline alloy, Fe—Cu—M′—Si—B (M ′ is a group consisting of Nb, W, Ta, Zr, Hf, Ti, and Mo described in Patent Document 1). The composition of the (at least one element selected) system is representative. In this composition system, the nucleation effect of the crystal phase by the addition of Cu and the effect of suppressing the growth of crystal grains by the addition of M ′ occur synergistically, and a structure including uniform and fine nanocrystal grains is formed. More specifically, a structure in which an amorphous phase remains around the Fe (-Si) crystal phase as the main layer is formed. The particle size of the nanocrystal phase is, for example, about 5 to 100 nm.

  The Fe-based nanocrystalline alloy is generally formed by heat-treating an amorphous (amorphous) alloy. The original amorphous alloy is produced by rapidly solidifying a liquid phase alloy (sometimes called a molten metal) heated to a melting point or higher. As a method for rapidly solidifying the molten metal, a single roll method, which is a method of discharging the molten alloy to a rotating cooling roll, is often employed.

  In the process of producing an annular magnetic core used for a common mode choke coil or the like, first, a ribbon-like amorphous alloy is produced from a molten alloy having a composition capable of obtaining an Fe-based nanocrystalline alloy by the single roll method described above. To do. The thickness of the amorphous alloy ribbon is, for example, 10 to 30 μm. Next, an annular wound body is formed by winding the amorphous alloy ribbon. Thereafter, the wound body is subjected to a heat treatment up to the crystallization temperature to precipitate microcrystals in the alloy structure (nanocrystallization), thereby obtaining an annular magnetic core made of the nanocrystalline alloy.

  The Fe-based nanocrystalline alloy exhibits a saturation magnetic flux density (for example, 1 T or more) comparable to the Fe-based amorphous alloy. In addition, the magnetic permeability is as high as that of the Co-based amorphous alloy over a wide frequency band, and the impedance in the high frequency band is also good. In recent years, high permeability / impedance characteristics in a frequency band of, for example, 100 kHz or more are often required to remove high-frequency noise. It is possible to remove noise.

Japanese Patent Publication No. 4-4393 JP 2007-103404 A

  By the way, common mode choke coils for in-vehicle use are required to have higher mechanical strength than other uses, particularly high vibration resistance and heat resistance against vibration.

  As a technique for improving the mechanical strength of a magnetic core, a method of impregnating a nanocrystal alloy wound body with a resin is known. By performing the resin impregnation, the mechanical strength of the wound body (magnetic core) weakened by the nanocrystallization heat treatment can be improved, and the vibration resistance can be improved.

  Patent Document 2 describes a technique for suppressing a decrease in impedance characteristics before and after a resin-impregnated magnetic core is subjected to a heating test. Specifically, the oxygen concentration in a nanocrystallization heat treatment atmosphere is set. It is disclosed to adjust to a range of 20 ppm to 100 ppm (particularly preferably, 25 ppm to 45 ppm). In this way, even if a heat test at 130 ° C. is performed on the resin-impregnated magnetic core after the heat treatment for nanocrystallization, a decrease in impedance characteristics before and after that is suppressed.

However, in recent years, in-vehicle use magnetic cores are required to have a magnetic core whose magnetic characteristics are not easily deteriorated even when used at a high temperature of 150 ° C. or higher (typically 160 ° C.). According to the study by the present inventors, when the heating test held at 150 ° C. or higher described later is performed on the magnetic core obtained by the manufacturing method described in Patent Document 2, the impedance relative permeability μ _rz is greatly reduced, the before and after the heating test of the 5% impedance relative magnetic permeability mu _rz rate of decrease in the frequency 100kHz, that impedance relative permeability mu _rz rate of decrease in frequency 1MHz exceeds 10% confirmed. Moreover, it was also confirmed that the resin-impregnated magnetic core is likely to deteriorate the impedance characteristics by this heating test.

  The present invention has been made in view of the above, and provides an Fe-based nanocrystalline alloy core suitable for use in a high-temperature environment of 150 ° C. or higher, a method for manufacturing the same, and a vehicle-mounted component including the magnetic core. With the goal.

A magnetic core according to an embodiment of the present invention is a magnetic core including a layered body of Fe-based nanocrystalline alloy ribbon and a resin impregnated in the layered body, and is heated from room temperature to a temperature of 160 ° C. in 20 minutes. When a heating test is performed in which the temperature is raised and then maintained for 500 hours and then air-cooled to room temperature, the rate of decrease in impedance relative permeability μ _rz at a frequency of 100 kHz is less than 5% before and after the heating test.

In one embodiment, before and after the heating test, the reduction rate of the impedance relative permeability μ _rz at a frequency of 1 MHz is 10% or less.

  In one embodiment, the emission intensity of oxygen by glow discharge analysis on the externally exposed surface and the opposite surface of the Fe-based nanocrystalline alloy ribbon of the outermost layer of the Fe-based nanocrystalline alloy ribbon layer is respectively determined. , O (out) and O (in), the relationship of O (out) / O (in)> 1.0 is established.

  An Fe-based nanocrystalline alloy magnetic core manufacturing method according to an embodiment of the present invention includes: a step of producing a layered body by winding or stacking nanocrystallizable Fe-based amorphous alloy ribbons; and the layered body having an oxygen concentration of 100 ppm or less. A first heat treatment step for precipitating nanocrystals in the layered body by heat treatment in a first atmosphere, and a layered body subjected to the first heat treatment step are oxidized more than the first atmosphere in the first heat treatment step. In a second atmosphere having a high concentration, a second heat treatment step of holding at a holding temperature of 100 ° C. or higher and lower than the nanocrystallization start temperature and a holding time of 1 hour or more and 24 hours or less and the second heat treatment step are performed. And impregnating the layered body with a resin.

  In one embodiment, in the second heat treatment step, the oxygen concentration of the second atmosphere is 0.1% to 50%, the holding temperature is 100 ° C. to 350 ° C., and the holding time is 1 hour or more and 10 hours or less.

  In one embodiment, in the first heat treatment step, the layered body of the Fe-based nanocrystalline alloy ribbon is heat treated at a maximum temperature of 580 ° C. or more and 600 ° C. or less.

  In one embodiment, after the first heat treatment step, before the second heat treatment step, further includes a relaxation step of applying an external force to the layer forming direction of the layered body and then releasing it.

According to an embodiment of the present invention, a resin-impregnated magnetic core in which a decrease in impedance relative permeability μ _rz in a high frequency band of 100 kHz or higher is suppressed before and after a heating test held at 160 ° C. is provided in a high temperature environment. A magnetic core that can be used for a long time is provided.

It is a manufacturing-process figure of the magnetic core by embodiment of this invention. It is a figure which shows an example of the temperature profile of the heat processing for nanocrystallization. It is an impedance relative permeability μ _rz (frequency 100 kHz) after a heating test in a magnetic core not impregnated with a resin of a comparative example. FIG. 6 is a result of GD-OES analysis on the exposed surface and the back surface of the outermost Fe-based nanocrystalline alloy ribbon of one of the magnetic cores of Example 6. FIG. FIG. 9 is a result of GD-OES analysis on the exposed surface and the back surface of the Fe-based nanocrystalline alloy ribbon of the outermost layer of the other magnetic core of Example 6. FIG. It is a GD-OES analysis result in the exposed surface and its back surface in the outermost Fe-based nanocrystalline alloy ribbon of one magnetic core of Example 12. It is a GD-OES analysis result in the exposed surface and its back surface in the outermost Fe-based nanocrystalline alloy ribbon of the other magnetic core of Example 12. It is a GD-OES analysis result in the surface of the exposed side, and the back surface in the Fe group nanocrystal alloy ribbon of the outermost layer of the magnetic core of a comparative example. It is impedance relative permeability μ _rz (frequency 100 kHz) after a heating test in a magnetic core corresponding to Patent Document 2 of a comparative example. It is an impedance relative permeability μ _rz (frequency 1 MHz) after a heating test in a magnetic core corresponding to Patent Document 2 of a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments described below.

The magnetic core of the present embodiment includes a layered body of an Fe-based nanocrystalline alloy ribbon and a resin impregnated in the layered body. The magnetic core is manufactured by a process that will be described in detail below, thereby suppressing a decrease in impedance relative permeability μ _rz at high temperatures in a high frequency band. Specifically, when a heating test is performed in which the temperature is raised from room temperature to 160 ° C. in 20 minutes and then held for 500 hours and then air-cooled to room temperature, impedance ratio transmission at a frequency of 100 kHz is performed before and after the heating test. The rate of decrease of magnetic _{susceptibility} μ _rz is suppressed to less than 5%.

The rate of decrease of the impedance relative permeability μ _rz is defined as μ _before the impedance relative permeability of the magnetic core before the heating test (after the resin impregnation and before heating), and μ _after the impedance relative permeability of the magnetic core after the heating test ( It is calculated by the formula of μ _before −μ _after ) / μ _before × 100 (%).

  FIG. 1 shows each manufacturing process in the manufacturing method of the magnetic core which is an example of embodiment of this invention.

  In this embodiment, first, as shown in step S1, an Fe-based amorphous alloy ribbon that is nanocrystallized by heat treatment is prepared. Next, as shown in step S2, the Fe-based amorphous alloy ribbon is wound to produce an annular wound body (layered body). A layered body may be formed by stacking a plurality of Fe-based amorphous alloy ribbons cut into strips or formed in an annular shape.

  Thereafter, as shown in step S3, the wound body is subjected to a first heat treatment step (heat treatment for nanocrystallization) in a first atmosphere in which the oxygen concentration is controlled to 100 ppm or less. Within a certain temperature range in the heat treatment, a magnetic field may be applied to the wound body together with the heat treatment (heat treatment in a magnetic field).

  Thereafter, as shown in step S4, it is preferable to perform a relaxation step in which an external force is applied to the wound body and then released.

  Furthermore, as shown in step S5, the second heat treatment step (at a temperature range of 100 ° C. or higher and lower than the crystallization start temperature in an oxidizing atmosphere containing oxygen with respect to the nanocrystallized wound body ( Heat treatment at a temperature lower than the first heat treatment temperature). The second heat treatment step is performed in a second atmosphere having a higher oxygen concentration than the first heat treatment step. The second heat treatment step is performed, for example, in an oxygen concentration atmosphere of 0.1% or more and 50% or less, preferably in the air.

  After performing this second heat treatment, as shown in step S6, a resin impregnation treatment for improving vibration resistance is performed on the nanocrystalline alloy wound body. Through step S6, the resin is impregnated between the ribbons of the layered body, and the resin is disposed between the layers of the Fe-based nanocrystalline alloy ribbon of the wound body and the surface of the wound body, thereby completing the magnetic core of the present embodiment.

  Hereinafter, each process S1-S6 in this embodiment is demonstrated more concretely.

  First, as shown in step S1, an Fe-based amorphous alloy ribbon that becomes a nanocrystalline alloy by heat treatment is prepared. The Fe-based amorphous alloy ribbon can be produced, for example, by a known single roll method. In the single roll method, a molten metal obtained by melting a raw material alloy is discharged onto a rotating roll and rapidly solidified to produce a ribbon-like amorphous alloy.

In the present embodiment, the nanocrystalline compounds gold constituting the Fe-based amorphous alloy or winding core, for _{example, (Fe 1-a M a} ) 100-xyz- α - β - γCu x Si y B z M'αM An alloy having a composition represented by “βXγ (atomic%) is applicable. Here, M is Co and / or Ni, and M ′ is Nb, Mo, Ta, Ti, Zr, Hf, V, Cr, At least one element selected from the group consisting of Mn and W, M ″ is at least one element selected from the group consisting of Al, platinum group elements, Sc, rare earth elements, Au, Zn, Sn, Re, X is at least one element selected from the group consisting of C, Ge, P, Ga, Sb, In, Be, and As. A, x, y, z, α, β, and γ are 0 ≦ a ≦ 0.5, 0.1 ≦ x ≦ 3, 0 ≦ y ≦ 30, 0 ≦ z ≦ 25, and 5 ≦ y + z ≦, respectively. 30, 0 ≦ α ≦ 20, 0 ≦ β ≦ 20 and 0 ≦ γ ≦ 20 are satisfied.

  Further, 0 ≦ a <0.1, 0.8 ≦ x ≦ 1.5, 14 ≦ y ≦ 20, 5 ≦ z ≦ 7, 2 ≦ α ≦ 5, 0 ≦ β ≦ 10 and 0 ≦ γ ≦ 10. When satisfied, it is easy to control the grain size of the crystal structure. This composition that can be easily controlled is preferably used when the heat treatment is performed at a maximum temperature of 580 ° C. or more and 600 ° C. or less in the first heat treatment step.

  By setting the composition as described above, it is possible to produce a wound body that becomes a nanocrystalline alloy stably in the first heat treatment step.

  The thickness of the Fe-based amorphous alloy ribbon may be about 10 μm to 30 μm, for example. When the thickness is less than 10 μm, the frequency of ribbon breakage during casting increases, and stable long-time casting is difficult, and the mechanical strength of the ribbon after casting may be insufficient. If the thickness exceeds 30 μm, cooling during rapid cooling is insufficient, and it may be difficult to stably form an amorphous phase. Moreover, since it uses for a high frequency use, in order to suppress the loss by generation | occurrence | production of an eddy current, the one where a ribbon is thinner is preferable. From this viewpoint, the thickness of the ribbon is preferably 10 to 20 μm, and more preferably 10 to 15 μm.

  The width of the amorphous alloy ribbon obtained in step S1 may be, for example, 10 mm to 100 mm. However, for the stable production of the alloy ribbon, the width of the ribbon is preferably 70 mm or less, and more preferably 60 mm or less. Note that a wide range of ribbons may be obtained by cutting (slit processing) wide alloy ribbons. In this way, productivity can be improved and cost reduction can be achieved.

  Next, a wound body is formed in step S2. In this step S2, the amorphous alloy ribbon obtained in step S1 is fixed to a columnar base that defines the inner peripheral diameter of the wound body, and the wound body (toroidal shape) is rotated by rotating the base. Is made. The diameter of the cylindrical base of the wound body (inner diameter of the wound body) may be, for example, 5 mm to 300 mm, and the outer diameter of the wound body may be, for example, 10 mm to 400 mm.

  Further, in step S2, instead of producing a wound body, the amorphous alloy ribbon is punched out using a die in a ring shape so that the outer diameter is less than the ribbon width (for example, outer diameter 50 mm, inner diameter 30 mm). A laminated body (layered body) may be produced by stacking a large number of ring-shaped alloy ribbons, and a magnetic core may be produced using this.

  In the present specification, a wound body obtained by winding a ribbon as described above, and a laminate obtained by stacking ribbons may be referred to as a “layered body”. The layered body only needs to have a layer structure, and a layer structure may be formed by winding and overlapping a series of ribbons like a wound body, or like a laminate, The layer structure may be formed by stacking a plurality of separated ribbons. Also, the direction in which the layer surfaces of the layered body overlap (typically the direction perpendicular to the layer surface), that is, the direction from the outer peripheral surface to the inner peripheral surface in the wound body, Sometimes referred to as the layer direction.

  In addition, it is preferable that the space factor (ratio of the ribbon which occupies for the lamination | stacking cross section of a layered body) of a layered body shall be 70 to 85%. If the space factor exceeds 85%, the number of electrical connection portions between the ribbons is likely to increase, and eddy current loss is likely to occur, so that the impedance relative permeability tends to decrease. On the other hand, when the space factor is less than 70%, since the ribbon of the layered body is easily displaced, it becomes difficult to handle the layered body during resin impregnation.

  Next, as shown in step S3, a first heat treatment step (heat treatment step for nanocrystallization) is performed on the manufactured wound body. When the Fe-based amorphous alloy having the above composition is heated to a temperature higher than the crystallization temperature, it can be nanocrystallized. Note that if the temperature is too high, the crystal becomes coarse and the nanocrystalline structure is not maintained, and therefore it is typically preferable to perform the first heat treatment at a maximum temperature of 550 ° C. to 600 ° C.

  FIG. 2 shows an example of a temperature profile (temperature curve) in the nanocrystallization heat treatment. In FIG. 2, the maximum temperature in the temperature profile is hereinafter referred to as a first heat treatment temperature. In the illustrated example, 585 ° C. is the first heat treatment temperature.

  In the example shown in FIG. 2, the temperature is raised from room temperature to 420 ° C. at a rate of 4.7 ° C./min, and then the temperature is raised to a maximum temperature of 585 ° C. at a rate of 0.7 ° C./min. ing. Thus, from room temperature to around 400 ° C., the temperature is increased relatively rapidly at a temperature increase rate of 3 to 7 ° C./min. By setting the heating rate to be relatively slow, nanocrystallization can be performed efficiently and stably. Here, on the way from the vicinity of 400 ° C. to the maximum temperature, a holding time at a predetermined temperature may be provided for about 20 minutes to 2 hours in the temperature range. Moreover, the frequency | count to hold | maintain may be 1 time or more. Further, in FIG. 2, the holding time at the maximum temperature is not provided, but the holding time at the maximum temperature may be provided for a maximum of about 1 hour. Further, in the cooling process after nanocrystallization, the cooling may be performed at a cooling rate of 2 to 15 ° C./min in the temperature range from the highest temperature to a low temperature of 200 ° C. Usually, after cooling to 100 ° C. or lower, the nanocrystallized wound body can be taken out into the atmosphere.

  In the range from the vicinity of 400 ° C. to the maximum temperature, the holding time at a predetermined temperature and the holding time at the maximum temperature are set in consideration of the heat capacity of the entire wound body to be heat-treated and the stability of characteristics. It is preferable.

  The heat treatment temperature is controlled by taking into consideration the capacity of the heat treatment furnace and the amount of heat generated by crystallization of the amorphous alloy ribbon to be heat treated, so that the actual temperature distribution in the heat treatment furnace becomes ± 5 ° C. or less. It is preferable to control as described above. By performing such control, the magnetic properties of the wound body after the heat treatment can be stabilized.

In the present embodiment, the first heat treatment step for nanocrystallization is performed in a first atmosphere in which the oxygen concentration is limited to 100 ppm or less. Examples of the first atmosphere to be used include inert gases such as Ar gas and N ₂ gas.

  As will be described later, in the present embodiment, since the second heat treatment step is performed in a second atmosphere having higher oxidizability than the first heat treatment step, the oxygen concentration in the first heat treatment step is, for example, 100 ppm or less, typically May be suppressed to 10 ppm or less or 5 ppm or less.

  In the first heat treatment step, the heat treatment may be performed while applying a DC magnetic field to the wound body in a predetermined temperature range. The application direction of the magnetic field is, for example, the axial direction of the wound body (the ribbon width direction). By applying a magnetic field in the axial direction of the wound body, magnetic anisotropy can be imparted and a characteristic in which a decrease in initial permeability is suppressed up to a high frequency region can be obtained. In addition, since magnetic characteristics, such as a squareness ratio, change according to the application direction of a magnetic field, you may apply a magnetic field to a different direction (for example, circumferential direction) according to a use.

  When a magnetic field is applied in the axial direction of the wound body, the strength of the applied magnetic field may be, for example, 50 kA / m to 300 kA / m (preferably 60 kA / m to 240 kA / m). When a magnetic field is applied in the circumferential direction of the wound body, the strength of the applied magnetic field may be, for example, 5 A / m or more and 30 A / m or less (preferably 6 A / m or more and 24 A / m). The time for applying the magnetic field is not particularly limited, but about 1 minute to 180 minutes is practical.

The application of the magnetic field may be selectively performed, for example, only in a temperature range from a temperature lower by 50 ° C. than the crystallization start temperature to a temperature higher by 50 ° C. than the crystallization start temperature. After passing through the temperature, it may be cooled to about 100 ° C. and may be carried out until just before taking out the wound body. The crystallization onset temperature can be identified by a differential scanning calorimeter (DSC). More specifically, the temperature at which DSC detects an exothermic reaction due to the start of nanocrystallization at the time of temperature rise can be regarded as the crystallization start temperature. Incidentally, the _{(Fe 1-a M a)} 100-xyz- α - β - in _{γCu x Si y B z M'αM "} βXγ Fe -based amorphous alloy having a composition represented by (atomic%), crystallization The starting temperature is about 480 ° C to about 500 ° C.

  Refer to FIG. 1 again. After the first heat treatment step shown in step S3, as shown in step S4, an external force is applied (applied) to the wound body subjected to the first heat treatment, and thereafter, an external force applied to the wound body. It is preferable to perform a step of releasing and relaxing. Normally, in the nanocrystallization heat treatment, the wound body contracts by about 1% due to crystallization of the amorphous alloy. Due to the shrinkage, a place where the layers of the alloy ribbon are fixed in an electrically connected state is generated. In order to relax this fixed location and reduce the electrical connection location, in step S4, pressure is applied in the radial direction of the wound body (direction in which layers are formed in the layered body: layer direction). The fixed portion is relaxed by applying and releasing the external force to the extent that the finger is pushed and then released, and after the relaxation, the layers can be somewhat slid in the axial direction (width direction). As a result, improvement of core loss can be expected.

  Thereafter, as shown in step S5, the second heat treatment step is performed in a more oxidizing atmosphere than the first heat treatment step on the wound body to which the external force is applied and released in step S4. The second heat treatment step is performed on the nanocrystallized alloy (rolled body) that has been cooled to 100 ° C. or lower after the first heat treatment step and taken out into the atmosphere to be at room temperature. As will be described in detail in the following examples, by performing the second heat treatment step, a decrease in impedance characteristics after the heating test is suppressed even in the magnetic core impregnated with the resin.

  The reason why the deterioration of impedance characteristics after the heating test is suppressed by the second heat treatment is presumed to be as follows.

  The Fe-based nanocrystalline alloy ribbon is manufactured by a single roll method, but there is a deviation in the thickness or there are irregularities on the surface. For this reason, in the case of a layered body, adjacent ribbons are not in contact with each other over the entire surface and are partially in point contact with each other, but the others are stacked via a gap. The resin is impregnated in the gap, and then cured by heating. The heat-cured resin is present on the ribbon surface in the form of spots or spots as viewed perpendicular to the ribbon surface. This is because the resin is impregnated in a state diluted with an organic solvent or the like, and the organic solvent volatilizes when the resin is dried. In this way, since the resin partially fixes the ribbons, when the resin shrinks in the heating test, the distance between the ribbons is shortened and the possibility of contact increases. In particular, the end side (lamination surface side) of the ribbon is most easily distorted because it is not restrained. If the end side of the ribbon comes into contact, the eddy current loss during energization tends to increase, and as a result, the impedance characteristics are likely to deteriorate.

  By performing the second heat treatment of the present invention before impregnating with the resin, since the ribbon has a gap between the ribbons, the surface of its end is oxidized. The end portions to be oxidized are oxidized not only on the end face of the ribbon but also on the end face sides of both sides of the ribbon. Since the surface of the oxidized end portion is insulative, as described above, even if the end portions of the ribbon are in contact with each other, the conduction is suppressed, and the occurrence of eddy current loss can be suppressed. As a result, the effect of the present invention Is presumed to be obtained.

  In the second heat treatment step, the heat treatment temperature (maximum temperature: sometimes referred to as the second heat treatment temperature) is 100 ° C. or higher and lower than the crystallization start temperature identified by the DSC. The second heat treatment temperature may be, for example, a temperature of 100 ° C. or higher and 350 ° C. or lower. When this temperature is less than 100 ° C., the effect of suppressing a decrease in impedance characteristics tends to be small. On the other hand, when the temperature is higher than 350 ° C., the direction of the magnetic domain is disturbed and the coercive force Hc tends to increase. A preferable temperature is in the range of 150 ° C. or higher and 330 ° C. or lower, and a more preferable temperature is in the range of 200 ° C. or higher and 300 ° C. or lower.

  Since the heat treatment temperature in the second heat treatment step is at most a temperature lower than the crystallization start temperature, it is lower than the maximum temperature in the first heat treatment step.

  The second heat treatment step is preferably performed in the atmosphere (oxygen concentration: about 20.9%), and is performed in an atmosphere having an oxygen concentration higher than at least the oxygen concentration in the heat treatment atmosphere in the first heat treatment step. .

  It is not realistic to perform the first heat treatment step in an atmosphere having a high oxygen concentration. This is because the first heat treatment step is a heat treatment for precipitating nanocrystals on the Fe-based nanocrystalline alloy ribbon, and therefore the temperature is 550 ° C. or higher. This is because the coercive force of the magnetic core obtained by being oxidized is increased. Therefore, in the present invention, a second heat treatment step is provided separately from the first heat treatment step, the temperature is set to 100 ° C. or higher and 350 ° C. or lower, which is lower than the first heat treatment step, and further in the heat treatment atmosphere in the first heat treatment step. In an atmosphere having an oxygen concentration higher than the oxygen concentration.

  The oxygen concentration in the heat treatment atmosphere in the second heat treatment step may be, for example, from 0.1% to 50%. In addition, since the magnetic field application is performed in the first heat treatment step, the second heat treatment step can be performed in the absence of a magnetic field.

  The holding time at the second heat treatment temperature may be, for example, 1 hour or more and 24 hours or less, and preferably 2 hours or more and 6 hours or less.

  The temperature profile in this step is not particularly limited. For example, the temperature in the oven containing the wound body is raised from room temperature to a second heat treatment temperature of 100 ° C. or more and 350 ° C. or less over 30 minutes to 1 hour, What is necessary is just to perform the process of hold | maintaining at 2 heat processing temperature for 2 hours-6 hours, and cooling to the temperature from 2nd heat processing temperature to less than 100 degreeC-room temperature over 2 hours-4 hours after that.

  In the second heat treatment performed in an atmosphere that is more oxidizing than the first heat treatment (preferably an atmosphere having an oxygen concentration of 0.1% to 50%), the surface of the alloy ribbon is oxidized. As shown in the following examples, according to the inventor's analysis, on the outermost alloy ribbon surface of the wound body, the oxide layer tended to be thickened by the second heat treatment. On the surface of the alloy ribbon, no phenomenon of thickening the oxide layer was observed.

  In the magnetic core of the present invention subjected to the second heat treatment, the exposed surface and the back surface of the Fe-based nanocrystalline alloy ribbon of the outermost layer are analysis values in glow discharge emission analysis (GD-OES). When the oxygen emission intensity on the exposed surface is O (out) and the oxygen emission intensity on the back surface is O (in), the following formula: O (out) / O (in)> 1 0 is satisfied. Further, this O (out) / O (in) can be set to 1.1 or more, and further 1.2 or more. Note that O (out) and O (in), which are measurement results of this GD-OES, are values obtained by measuring the maximum value of the emission intensity of oxygen in the range of 30 nm or less from the surface of the ribbon.

  Thereafter, resin impregnation is performed as shown in step S6 of FIG. As the resin to be impregnated, an epoxy resin or an acrylic resin can be used as appropriate. Moreover, as a solvent used when impregnating resin, acetone can be used, for example.

  The ratio of the resin mass to the total mass of the resin and the solvent (that is, the resin content in the solvent containing the resin) is preferably about 5 mass% to 40 mass%, more preferably 7 mass% to 30 mass%, still more preferably, It is 10 mass%-30 mass%.

  The impregnation treatment can be performed, for example, by immersing the wound body in a resin solution in which an uncured resin and a solvent are mixed for about 30 seconds to 5 minutes under normal temperature and atmospheric pressure conditions. Moreover, you may perform the hardening process after resin impregnation by heating to the temperature of 100 degreeC or more, after leaving to stand in normal temperature air | atmosphere.

  By the steps S1 to S6 described above, a magnetic core having high vibration resistance and excellent magnetic properties can be produced by resin impregnation.

  Normally, a coil or transformer is manufactured by winding a conductive wire around a magnetic core. However, if the conductive wire is directly wound around a magnetic core wound with an alloy ribbon, the insulation between the alloy ribbon and the conductive wire may be insufficient. Moreover, there is a possibility that the conducting wire may be broken or broken at the edge of the magnetic core. For this reason, it is common practice to wind the conducting wire with the magnetic core stored in the resin case. Therefore, after step S6, the wound core impregnated with resin may be stored and accommodated in the case. For example, a common mode choke coil can be manufactured by housing a wound magnetic core in an annular case made of engineering plastic and winding a conductive wire forming the coil through the case. As the engineering plastic, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), etc. mixed with glass filler can be used. The magnetic core in the case is preferably fixed by a silicon-based adhesive filled between the case inner side and the magnetic core. If the magnetic core in the case is not fixed, the magnetic core and the case may come into contact with each other due to vibration or impact, and part of the surface of the magnetic core may be damaged.

As a characteristic index of the common mode choke coil, the impedance relative permeability μ _rz is often used. Impedance relative permeability μ _rz is the voltage (magnetic flux density) generated on the secondary side by mutual inductance when an alternating current (equivalent to magnetizing force) is passed through the primary winding in a closed magnetic circuit core where leakage flux can be ignored. Relative permeability calculated from the above. This index is expressed by the following formula as described in JIS standard C2531 (revised in 1999). As can be seen from the following equation, the impedance relative permeability μ _rz is equal to the absolute value of the complex permeability.
μ _rz = (μ _{r '} ² + μ _{r "} ² ) ^1/2

In this specification, the impedance relative permeability μ _rz is measured using Agilent 4194A, and the measurement conditions are the transmission output voltage OSC = 0.5 V, AVG 8, and RX mode.

If the impedance relative permeability μ _rz is a high value in a wide frequency band, the ability to absorb and remove common mode noise in a wide frequency band is excellent.

  In particular, when the magnetic core of the present embodiment is left in a high temperature environment of 150 ° C. or higher for a long time, a decrease in impedance relative permeability is suppressed in a high frequency band of 100 kHz or higher. Therefore, it is suitably used particularly in fields such as in-vehicle use where vibration resistance and heat resistance are required.

More specifically, in the magnetic core according to the present embodiment, the rate of decrease in the impedance relative permeability μ _rz at a frequency of 100 kHz may be less than 5% before and after a heating test including a process of holding at 160 ° C. for 500 hours. it can. In addition, the rate of decrease in impedance relative permeability μ _rz at a frequency of 1 MHz can be reduced to 10% or less before and after the heating test. More specifically, the above heating test is a heating test in which the temperature is raised from room temperature to a temperature of 160 ° C. over 20 minutes in the air over 20 minutes, then held for 500 hours, and then air-cooled to room temperature. The step of air cooling to room temperature may be performed by, for example, leaving the magnetic core at 160 ° C. for 500 hours and then leaving it in the atmosphere for 24 hours.

  Examples of the present invention and comparative examples will be described below.

Example 1
An alloy melt having an alloy composition of Fe: bal, Cu: 1.0, Nb: 3.0, B: 6.5, Si: 15.5 (both numbers indicate atomic% and bal indicates the remainder). Then, it was rapidly solidified by a single roll method to produce an alloy ribbon having a thickness of 13 μm and a width of 52 mm. The manufactured alloy ribbon was slit to obtain 5 ribbons having a width of 10 mm. An alloy ribbon having a width of 10 mm after slit processing was wound to prepare two wound bodies (samples A and B) having an inner diameter of 21 mm, an outer diameter of 31 mm, and a height of 10 mm. Moreover, when winding the ribbon, the space factor of the wound body was adjusted to 75% by adjusting the tension. The start and end of winding were fixed to the adjacent alloy ribbon by spot welding.

  Next, a first heat treatment (heat treatment in a nanocrystallization magnetic field) as shown in FIG. 2 was performed on the two wound bodies to obtain a nanocrystalline alloy. The maximum temperature (first heat treatment temperature) was 595 ° C. In the temperature range of 480 ° C. to 530 ° C., a magnetic field of 130 kA / m was applied in the axial direction of the wound body (the width direction of the alloy ribbon). The first heat treatment was performed in a nitrogen atmosphere, and the oxygen concentration was 5 ppm.

  Next, after the first heat treatment, the wound body was cooled to room temperature, and the wound body taken out to the atmosphere was subjected to a step of pushing with a finger from the diameter direction to relax the fixing portion between adjacent alloy ribbons.

  Next, the wound body was put in an air atmosphere oven, heated to 250 ° C. in 30 minutes, held at 250 ° C. for 4 hours, and then subjected to a second heat treatment with a temperature profile cooled to 100 ° C. in 3 hours.

  Next, the wound body was impregnated with resin. The wound body was immersed in a resin solution (mass ratio: epoxy resin / acetone = 10/90) in which an epoxy resin and acetone were mixed. After being immersed for 1 minute at room temperature, the wound body was taken out of the solution, and the solution on the surface of the wound body was removed. Further, after being left at room temperature for 1 hour, the epoxy resin was cured by heating at 150 ° C. for 15 minutes in an air atmosphere oven. The magnetic core was produced by the above process.

  Next, the magnetic core after the resin impregnation was stored in a case made of PET (polyethylene terephthalate) mixed with glass filler. The magnetic core and the inside of the case were fixed with a silicon adhesive.

Next, a coil of one turn was wound on the magnetic core stored and fixed in the resin case from above the resin case, and the impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured. The measuring machine used was Agilent 4194A. The measurement conditions were OSC 0.5V, AVG 8, RX mode.

Next, the magnetic core is stored in an oven in an air atmosphere, heated from room temperature to 160 ° C. in 20 minutes, then held for 500 hours, and then left in the air for 24 hours to cool to room temperature. A test was conducted. After this heating test, the impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature in the same manner as before the heating test.

Table 1 shows the results of the measurement and the ratio (%) of the measured value after the heating test described in <> where the measured value of the impedance relative permeability μ _rz after impregnation with the resin is 100. . Table 2 shows the decrease rate of the impedance relative permeability μ _rz for each sample after the heating test and before the heating test. In Tables 1 and 2, the results of Comparative Example 1, Example 2, and Example 3 described later are similarly shown.

As shown in Table 2, with regard to the impedance relative permeability μ _rz having a frequency of 100 kHz, attention is paid to the rate of decrease before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours. Then, the reduction rate is as small as 1% or 2%.

In addition, regarding the impedance relative permeability μ _{rz having} a frequency of 1 MHz, when attention is paid to the rate of decrease before and after the above heating test including high temperature standing at 160 ° C. for 500 hours, in the samples A and B of Example 1, 3% or The reduction rate is as small as 4%.

(Comparative Example 1)
Without performing the second heat treatment at 250 ° C. for 4 hours described in Example 1 (omitted), the other steps were performed in the same manner as in Example 1 to prepare two magnetic cores (samples C and D). Similarly to Example 1, the above heating test including the step of holding at 160 ° C. for 500 hours was performed, and then the impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results are shown in Tables 1 and 2 above.

With regard to the impedance relative permeability μ _{rz having} a frequency of 100 kHz, paying attention to the rate of decrease before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, in the samples A and B of Example 1, 1% or 2% On the other hand, the decrease rate is as small as 14% or 16% in the samples C and D of Comparative Example 1.

In addition, regarding the impedance relative permeability μ _{rz having} a frequency of 1 MHz, when attention is paid to the rate of decrease before and after the above heating test including high temperature standing at 160 ° C. for 500 hours, in the samples A and B of Example 1, 3% or While the decrease rate is as small as 4%, the samples C and D of Comparative Example 1 are large as 27% or 31%.

(Comparative Example 2)
A manufacturing method in which the second heat treatment at 250 ° C. described in Example 1 for 4 hours is not performed (omitted) and the first atmosphere of the first heat treatment is set to an oxygen concentration of 35 ppm (manufacturing corresponding to Patent Document 2) The wound body was manufactured by the method.

  The alloy ribbon used had a width of 20 mm. This alloy ribbon was wound into a wound body having an inner diameter of 45 mm, an outer diameter of 60 mm, and a height of 20 mm, and six such wound bodies were manufactured.

   Next, a first heat treatment (heat treatment in a nanocrystallization magnetic field) as shown in FIG. 2 is performed in the same manner as in Example 1 except that the six wound bodies are in a nitrogen atmosphere with an oxygen concentration of 35 ppm. To obtain a nanocrystalline alloy.

  Thereafter, the second heat treatment was not performed (omitted), and the wound body and the magnetic core were produced in the same manner as in Example 1 in the other steps. Thereafter, a heating test of the magnetic core was performed. The heating test was performed in the same manner as in Example 1 except that the temperature to be held was 155 ° C.

  The results are shown in FIGS. FIG. 9 shows the measurement results at a frequency of 100 kHz, and FIG. 10 shows the measurement results at a frequency of 1 MHz. The points plotted in FIGS. 9 and 10 are the average values of the measured values of the six magnetic cores produced.

As shown in FIG. 9, when the impedance relative permeability μ _rz with a frequency of 100 kHz is focused on the decrease rate before and after the above heating test including high temperature _exposure at 155 ° C. for 500 hours, the decrease rate exceeds 15%. (15.7%).

Also, as shown in FIG. 10, when focusing on the rate of decrease in impedance relative permeability μ _rz at a frequency of 1 MHz before and after the above heating test including high temperature _exposure at 155 ° C. for 500 hours, the rate of decrease is 25%. (29.0%).

  The result of these heating tests is a holding temperature of 155 ° C. Therefore, if the holding temperature of the heating test is performed at 160 ° C., which is the same as in Example 1, it is clear that the decrease rate is further increased.

(Examples 2 and 3)
In Example 1, the first heat treatment is performed at the maximum temperature of 595 ° C., but in Example 2, the maximum temperature is set to 590 ° C., in Example 3, the first temperature is set to 585 ° C., and the other steps are performed. In the same manner as in Example 1, two magnetic cores (590 ° C .: Samples E and F) (585 ° C .: Samples G and H) were produced. Further, in the same manner as in Example 1, after conducting a heating test including a step of holding at 160 ° C. for 500 hours, impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results are shown in Tables 1 and 2 above.

_Focusing on the decrease rate before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, the impedance relative permeability μ _{rz at} a frequency of 100 kHz is 1% or 2% in Example 1, and 2% in Example 2. 2% and 3% in Example 3, both of which are small reduction rates.

Further, regarding the impedance relative permeability μ _{rz having} a frequency of 1 MHz, focusing on the rate of decrease before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, in Example 1, 3% or 4% 2 is 4% and Example 3 is 7%, both of which are small reduction rates.

Example 4
An alloy ribbon was prepared in the same manner as in Example 1 except that the alloy ribbon width was 25 mm. The produced alloy ribbon was wound to produce two magnetic cores (samples I and J) having an inner diameter of 21 mm, an outer diameter of 31 mm, and a height of 25 mm, and the subsequent processes such as the first heat treatment were performed in the same manner as in Example 1. .

In the same manner as in Example 1, after conducting a heating test including a step of holding at 160 ° C. for 500 hours, impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results and the reduction rate of the impedance relative permeability μ _rz are shown in Tables 3 and 4 below.

In Table 3, as in Table 1, the measured value of impedance relative permeability μ _rz after impregnation with resin is defined as 100, and the ratio (%) of the measured value after the heating test is described in <>. ing. Table 4 shows the rate of decrease in the impedance relative permeability μ _rz after the heating test and before the heating test, as in Table 2.

_Focusing on the reduction rate before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, the impedance relative permeability μ _{rz at} a frequency of 100 kHz is a low reduction rate of 3% in Example 4.

Further, regarding the impedance relative permeability μ _{rz at} a frequency of 1 MHz, focusing on the decrease rate before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, in Example 4, the decrease is as small as 6% or 9%. Rate.

(Example 5)
In the same manner as in Example 1, a 52 mm wide alloy ribbon was produced. The produced alloy ribbon was slitted to a width of 25 mm. The alloy ribbon after the slit processing is wound to produce two magnetic cores (samples K and L) having an inner diameter of 21 mm, an outer diameter of 31 mm, and a height of 25 mm. went.

In the same manner as in Example 1, after conducting a heating test including a step of holding at 160 ° C. for 500 hours, impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results are shown in Table 3 and Table 4 below.

_Focusing on the rate of decrease in impedance relative permeability μ _{rz at} a frequency of 100 kHz before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, in Example 5, the rate of decrease was as small as 3%.

Further, regarding the impedance relative permeability μ _{rz having} a frequency of 1 MHz, focusing on the rate of decrease before and after the above heating test including high temperature standing at 160 ° C. for 500 hours, in Example 5, the decrease is as small as 5% or 8%. Rate.

  When Example 4 is compared with Example 5, no significant difference in characteristics is observed with and without slitting.

(Comparative Example 3)
As in Comparative Example 1, the other heat treatments were performed in the same manner as in Example 1 except that the second heat treatment at 250 ° C. for 4 hours was not performed (omitted) and the resin was not impregnated. Produced. After performing the same heating test as in Example 1 held at 160 ° C. for 1 hour, 100 hours, 200 hours, and 500 hours, the impedance relative permeability μ _rz at a frequency of 100 kHz was measured at room temperature. The result is shown in FIG. In addition, the point plotted in FIG. 3 is an average value of the measured values of five manufactured magnetic cores.

As shown in FIG. 3, with regard to the impedance relative permeability μ _rz having a frequency of 100 kHz, paying attention to the rate of decrease before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, the rate of decrease is only 3% ). That is, in the magnetic core not impregnated with the resin, the impedance relative permeability μ _rz after the heating test at a frequency of 100 kHz is less than 5% even after 500 hours, and it is difficult to decrease in the first place.

On the other hand, in the case of the resin-impregnated magnetic core, as shown in Comparative Examples 1 and 2, when the second heat treatment is not performed, the reduction rate of the impedance relative permeability μ _rz after the heating test greatly exceeds 10% ( 14%, 15%).

From this, it can be seen that the resin-impregnated magnetic core has a higher rate of decrease in impedance relative permeability μ _rz due to the heating test than that without the resin impregnation.

(Example 6)
In Example 1, an alloy ribbon having a width of 10 mm is wound to form a wound body having an inner diameter of 21 mm, an outer diameter of 31 mm, and a height of 10 mm. However, in Example 6, the outer diameter is changed to have an inner diameter of 21 mm and an outer diameter of 26 mm. A wound body having a height of 10 mm was obtained. Other processes were the same as in Example 1, and two magnetic cores (samples M and N) were produced. Further, in the same manner as in Example 1, after conducting a heating test including a step of holding at 160 ° C. for 500 hours, impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results are shown in Tables 5 and 6 below.

As shown in Table 6, with regard to the impedance relative permeability μ _rz having a frequency of 100 kHz, when attention is paid to the decrease rate before and after the above heating test including high temperature standing at 160 ° C. for 500 hours, the samples M and N of Example 6 Is a reduction rate as small as 2% or 3%.

Further, regarding the impedance relative permeability μ _{rz having} a frequency of 1 MHz, when attention is paid to the rate of decrease before and after the heating test including high-temperature standing at 160 ° C. for 500 hours, the samples M and N of Example 6 are 6% or The reduction rate is as small as 7%.

(Examples 7 and 8)
In Example 6 described above, the second heat treatment is performed in an air atmosphere. In Example 7, the oxygen concentration was 1%, and in Example 8, the oxygen concentration was 5%. The other steps were performed in the same manner as in Example 6 to prepare two magnetic cores (oxygen concentration 1%: samples O and P) (oxygen concentration 5%: samples Q and R). Further, in the same manner as in Example 6, after conducting a heating test including a step of holding at 160 ° C. for 500 hours, impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results are shown in Table 7 and Table 8 below.

As shown in Table 8, with regard to the impedance relative permeability μ _rz having a frequency of 100 kHz, focusing on the rate of decrease before and after the above heating test including standing at 160 ° C. for 500 hours, the samples O and P of Example 7 And in the samples Q and R of Example 8, the decrease rate is as small as 2%.

Further, regarding the impedance relative permeability μ _{rz having} a frequency of 1 MHz, when attention is paid to the decrease rate before and after the above heating test including high temperature standing at 160 ° C. for 500 hours, the samples O and P of Example 7 and Example In the samples Q and R of 8, the decrease rate is as small as 7% or 8%.

(Examples 9 to 13)
In the above Example 6, the second heat treatment is performed in a temperature profile in which heating is performed to 250 ° C. in 30 minutes, holding at 250 ° C. for 4 hours, and then cooling to 100 ° C. in 3 hours. Conducted experiments by changing the holding temperature and holding time. Specifically, in Example 9, heating was performed to 200 ° C. in 30 minutes, held at 200 ° C. for 4 hours, and then cooled to 100 ° C. in 3 hours. In Example 10, the temperature profile was heated to 300 ° C. in 30 minutes, held at 300 ° C. for 4 hours, and then cooled to 100 ° C. in 3 hours. In Example 11, the temperature profile was heated to 200 ° C. in 30 minutes, held at 200 ° C. for 24 hours, and then cooled to 100 ° C. in 3 hours. In Example 12, the temperature profile was heated to 250 ° C. in 30 minutes, held at 250 ° C. for 24 hours, and then cooled to 100 ° C. in 3 hours. In Example 13, the temperature profile was set to 300 ° C. in 30 minutes, held at 300 ° C. for 24 hours, and then cooled to 100 ° C. in 3 hours. The other steps were the same as in Example 6. Two magnetic cores (holding temperature 200 ° C., 4 hours hold: samples S and T) (holding temperature 300 ° C., 4 hours hold: samples U and V) (holding temperature 200 C., hold for 24 hours: Samples W and X) (holding temperature 250.degree. C., hold for 24 hours: Samples: Samples Y and Z) (holding temperature 300.degree. C., hold for 24 hours: Samples AA and AB). Further, in the same manner as in Example 6, after conducting a heating test including a step of holding at 160 ° C. for 500 hours, impedance relative permeability μ _rz at frequencies of 100 kHz and 1 MHz was measured at room temperature. The results are shown in Table 9 and Table 10. For reference, Table 9 and Table 10 also show the measurement results of the sample of Example 6 (holding temperature 250 ° C., holding for 4 hours: sample: samples M and N).

As shown in Table 10, with regard to the impedance relative permeability μ _rz having a frequency of 100 kHz, focusing on the rate of decrease before and after the above heating test including high temperature _exposure at 160 ° C. for 500 hours, Samples S, T, U, V, W, X, Y, Z, AA, and AB have a small reduction rate of 1% to 4%.

Further, with regard to the impedance relative permeability μ _{rz having} a frequency of 1 MHz, focusing on the rate of decrease before and after the above heating test including high temperature standing at 160 ° C. for 500 hours, the samples S, T, U, V, W, X, Y, Z, AA and AB are small reduction rates of 4% to 8%. In particular, the sample of Example 13 (retention temperature 300 ° C., retention for 24 hours: Samples AA and AB) has a low decrease rate of 4% or 5%.

(Example 14)
The outer surface of the outermost layer (outermost circumference) Fe-based nanocrystalline alloy ribbon of the wound body of Example 6 (second heat treatment (held at 250 ° C. for 4 hours) and then resin-impregnated wound body) The composition of the exposed surface (hereinafter, exposed surface) and the opposite surface (hereinafter, back surface) were analyzed. The analysis was performed using glow discharge luminescence analysis (GD-OES: GD-PROFILER2 manufactured by Horiba). The measurement conditions were a gas pressure of 600 Pa, an output of 35 W, a pulse mode, and an anode diameter of 2 mm. The elements to be measured were Fe, Ni, Cu, Si, O, C, and B.

  FIG. 4 is a GD-OES analysis result on the exposed surface and the back surface of one of the two wound bodies measured. The analyzed light emission intensity of oxygen is obtained by measuring the light emission intensity of oxygen obtained under the above measurement conditions with a sputtering time of 1 second or less.

  As shown in FIG. 4, the maximum value of the light emission intensity of oxygen on the exposed surface (peak light emission intensity O (out)) was 0.56. Further, the maximum value of the light emission intensity of oxygen on the back surface (peak light emission intensity O (in)) was 0.35. The ratio of peak emission intensity, O (out) / O (in), was 1.6.

  FIG. 5 is a GD-OES analysis result on the exposed surface and the back surface of the other wound body. The maximum value of the luminescence intensity of oxygen on the exposed surface (peak luminescence intensity O (out)) was 0.44. Further, the maximum value of the light emission intensity of oxygen on the back surface (peak light emission intensity O (in)) was 0.32. The ratio of peak emission intensity, O (out) / O (in), was 1.4.

(Example 15)
The wound body of Example 12 (second heat treatment (held at 250 ° C. for 24 hours), and then a resin-impregnated wound body) of the outermost Fe-based nanocrystalline alloy ribbon of the two outermost layers (outermost circumference) In the same manner as in Example 12, the composition of the exposed surface (hereinafter, exposed surface) and the opposite surface (hereinafter, back surface) were analyzed.

  FIG. 6 shows a GD-OES analysis result on the exposed surface and the back surface of one of the two measured windings. The maximum value of the light emission intensity of oxygen on the exposed surface (peak light emission intensity O (out)) was 0.42. Further, the maximum value of the light emission intensity of oxygen on the back surface (peak light emission intensity O (in)) was 0.26. The ratio of peak emission intensity, O (out) / O (in), was 1.6.

  FIG. 7 shows GD-OES analysis results on the exposed surface and the back surface of the other wound body. The maximum value of the light emission intensity of oxygen on the exposed surface (peak light emission intensity O (out)) was 0.42. Further, the maximum value of the light emission intensity of oxygen on the back surface (peak light emission intensity O (in)) was 0.35. The ratio of peak emission intensity, O (out) / O (in), was 1.2.

(Comparative Example 4)
A wound body of Comparative Example 1 (a wound body manufactured without performing the second heat treatment (omitted) and other processes manufactured in the same manner as in Example 1) was prepared, and exposed in the same manner as in Example 14. The GD-OES analysis of the surface and the back surface was performed.

  FIG. 8 shows GD-OES analysis results on the exposed surface and the back surface of the magnetic core of Comparative Example 4.

  As shown in FIG. 8, the maximum value of the light emission intensity of oxygen on the exposed surface (peak light emission intensity O (out)) was 0.27. Further, the maximum value of the light emission intensity of oxygen on the back surface (peak light emission intensity O (in)) was 0.30. The ratio of peak emission intensity, O (out) / O (in), was 0.9.

(Discussion)
From the results of Examples 1 to 14 and Comparative Examples 1 and 2, it can be seen that even when the magnetic core is impregnated with the resin, the decrease in the impedance relative permeability μ _rz in a high temperature environment can be suppressed by performing the second heat treatment. Therefore, according to the present disclosure, it has been found that a magnetic core having improved mechanical strength due to the impregnated resin and in which a decrease in impedance relative permeability at a high temperature due to the second heat treatment is suppressed can be obtained. In addition, the results of Comparative Example 3 show that the impedance relative permeability μ _rz is unlikely to decrease after the heating test unless the magnetic core is impregnated with resin. That is, it is necessary to use the manufacturing method of the present invention when manufacturing a magnetic core impregnated with a resin.

In particular, the magnetic core according to the embodiment of the present invention can be expected to maintain a high impedance relative permeability μ _rz even when used for a long period of time in a high temperature environment of 160 ° C., and is preferably used as a vehicle-mounted component. .

  In addition, from the results of Examples 14 and 15 and Comparative Example 4, whether or not the second heat treatment step was performed was determined based on whether or not oxygen was determined by glow discharge analysis on the outermost exposed surface and the opposite surface of the outermost layer of the magnetic core. It can be seen that the intensity can be determined by measuring the emission intensity. In the second heat treatment step, the heat treatment is performed in an atmosphere having a higher oxygen concentration than in the first heat treatment step, so that the surface exposed to the outside of the outermost layer is oxidized more than the opposite surface by performing the second heat treatment. . In Examples 14 and 15, since the second heat treatment is performed, the emission intensity of oxygen by glow discharge analysis on the surface exposed to the outside of the outermost layer and the surface on the opposite side is respectively O (out) and O (in ), O (out) / O (in) exceeds 1. On the other hand, in Comparative Example 1, since the second heat treatment is not performed, O (out) / O (in) is less than 1.

  The magnetic core according to the embodiment of the present invention is particularly preferably used as a magnetic core for an in-vehicle common mode choke coil.

S1 Step of preparing Fe-based amorphous ribbon S2 Step of forming wound body (layered body) S3 First heat treatment (nanocrystallization heat treatment) step S4 Step of applying and releasing force from outside S5 Second heat treatment (first heat treatment) Heat treatment at lower temperature) Step S6 Resin impregnation treatment step

Claims (8)

A magnetic core comprising a layered body of Fe-based nanocrystalline alloy ribbon and a resin impregnated in the layered body,
In the atmosphere, when the heating test was performed in which the temperature was raised from room temperature to 160 ° C. in 20 minutes and then held for 500 hours and then air-cooled to room temperature, impedance ratio transmission at a frequency of 100 kHz was performed before and after the heating test. A magnetic core having a decrease rate of magnetic _{susceptibility} μ _rz of less than 5%. The magnetic core according to claim 1, wherein the rate of decrease in impedance relative permeability μ _rz at a frequency of 1 MHz is 10% or less before and after the heating test.   The emission intensity of oxygen by glow discharge analysis on the surface exposed to the outside and the opposite surface of the Fe-based nanocrystalline alloy ribbon of the outermost layer of the layered body of the Fe-based nanocrystalline alloy ribbon is O (out), respectively. The magnetic core according to claim 1, wherein a relationship of O (out) / O (in)> 1.0 is established when O and O (in).   A vehicle-mounted component including the magnetic core defined in any one of claims 1 to 3. Winding or stacking nanocrystallizable Fe-based amorphous alloy ribbons to produce a layered body;
A first heat treatment step of depositing nanocrystals in the layered body by heat-treating the layered body in a first atmosphere having an oxygen concentration of 100 ppm or less;
The layered body on which the first heat treatment step has been performed, in a second atmosphere having a higher oxidizing property than the first atmosphere in the first heat treatment step, a holding temperature of 100 ° C. or higher and lower than the nanocrystallization start temperature, and A second heat treatment step for holding at a holding time of 1 hour to 24 hours;
A method for producing an Fe-based nanocrystalline alloy magnetic core, comprising an impregnation step of impregnating a resin into a layered body that has been subjected to the second heat treatment step.   In the second heat treatment step, the oxygen concentration of the second atmosphere is 0.1% to 50%, the holding temperature is 100 ° C. to 350 ° C., and the holding time is 1 hour to 10%. The production method according to claim 5, wherein the production time is less than or equal to the time.   The manufacturing method according to claim 5, wherein the first heat treatment step heats the layered body of the Fe-based nanocrystalline alloy ribbon at a maximum temperature of 580 ° C. or more and 600 ° C. or less.   8. The method according to claim 5, further comprising a relaxation step of applying an external force to the layer direction of the layered body and then releasing it after the first heat treatment step and before the second heat treatment step. Manufacturing method.

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