JP2002075718A - Soft magnet thin plate, iron core formed of the same, current transformer, and method of manufacturing iron core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic thin plate having superior soft magnetic characteristics, magnetic core using the same, a current transformer, and to provide a method of manufacturing the magnetic core. SOLUTION: A soft magnetic thin plate is formed on Fe-based nanocrystal alloy which contains 3 atm.% or lower Cu and has a structure composed of fine crystal grains 100 nm or lower in grain diameter. Fe is higher in atom concentration than oxygen in terms of SiO2 at a point deeper than 10 nm from the surface of the above soft magnetic thin plate, and Cu has its peak atom concentration at a point deeper than 5 nm from the surface of the thin plate. The above soft magnetic thin belts are laminated into a magnetic core, and a current transformer is formed by the use of the magnetic core. For instance, Fe-based amorphous ribbons, realizing a nanocrystal structure and containing 3 atm.% or lower Cu are laminated into the laminate. The laminate is heated and subjected to a crystallization treatment in an atmosphere of nonreactive gas for the formation of the magnetic core. Fe is higher in atom concentration than oxygen in terms of SiO2 at a point deeper than 10 nm from the surface, and Cu has its peak atom concentration at a point deeper than 5 nm from the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin plate made of a nanocrystalline alloy having a surface layer composition controlled by heat treatment to impart excellent soft magnetic properties, a magnetic core made of the thin plate, a current transformer, and a method of manufacturing a magnetic core. .

[0002]

2. Description of the Related Art Thin plates having soft magnetic characteristics are mainly laminated and used as a magnetic core, and are incorporated in a current transformer, a magnetic amplifier and the like. For example, a current transformer is a type of current sensor, and is used for current measurement, an earth leakage breaker, and the like. FIG. 1 shows an example of the configuration. The current transformer generally has a winding 2 passing through a closed magnetic path composed of a ring-shaped magnetic core as shown in FIG. 1 and a wire 1 through which a current to be measured flows passes therethrough, and is output to the winding 2 by the current flowing through this wire. It measures the current flowing through the line 1 from the voltage, and is generally used in a frequency band of several hundred Hz at most from the commercial frequency. As the above magnetic core, there is almost no thermal instability seen in the amorphous alloy, little change over time, a thin sheet of Fe-based nanocrystalline alloy having low magnetostriction and high magnetic permeability is wound in a toroidal shape, or stamped and laminated. It is shown in patent 2501860 that these are preferred. Since the Fe-based nanocrystalline alloy proposed here has a higher saturation magnetic flux density than permalloy and Co-based amorphous alloy, it is also effective in that the range of measurable current is large.

A typical composition of the above-mentioned Fe-based nanocrystalline alloy is a Fe-based nanocrystalline alloy described in JP-B-4-4393 and JP-B-7-74419.
-Si-B- (Nb, Ti, Hf, Mo, W, Ta) -Cu alloy and Fe-
(Co, Ni) -Cu-Si-B- (Nb, W, Ta, Zr, Hf, Ti, M
o) Alloys and the like are known. As a method for producing these Fe-based nanocrystalline alloys, a method is known in which an amorphous alloy obtained by quenching the above alloy from a liquid phase or a gas phase is heat-treated and crystallized to refine crystal grains. ing. As a quenching method from a liquid phase, a single roll method, a twin roll method, an atomizing method, a spinning method in a rotating liquid, and the like are known.
As a quenching method from a gas phase, a sputtering method, an evaporation method, and the like are known.

[0004]

In the above-mentioned current transformer and the like, further improvement of the magnetic permeability of the magnetic core used for the closed magnetic circuit is required especially in order to reduce the size and cost of the device. The improvement of the magnetic permeability not only improves the sensitivity to the current to be measured, but also makes it possible to reduce the size of the magnetic core and to reduce the number of turns of the winding around the magnetic core. An object of the present invention is to provide a method of manufacturing a thin plate and a core made of the thin plate having excellent soft magnetic properties by controlling the composition of the surface layer by heat treatment with a nanocrystalline alloy, and a magnetic core having excellent soft magnetic properties. is there.

[0005]

Means for Solving the Problems The present inventors have found that the fluctuation of the magnetic permeability of a nanocrystalline alloy is extremely sensitive to the concentration of each atom on the alloy surface, and have determined the relationship between the surface element concentration and the magnetic permeability. It was found that it was important that the oxygen concentration at a certain depth from the surface be lower than the Fe concentration and that a peak of the Cu concentration be recognized at a certain depth or more from the surface. That is, the present invention contains 3% or less by atomic% of Cu,
m is composed of nanocrystalline alloy of Fe group having the fine crystal grains consisting tissues and 5nm at a position deeper than 10nm from the surface in terms of SiO _2, a high concentration of Fe than the oxygen, from the surface in terms of SiO ₂ This is a soft magnetic thin plate in which a peak of the atomic concentration of Cu is recognized at a deeper position. The magnetic core is formed by laminating the soft magnetic thin plates of the present invention.

The above-described thin plate or magnetic core of the present invention is obtained by heating an amorphous ribbon capable of expressing a nanocrystalline structure in a non-reactive gas atmosphere, for example, in a ribbon state or in a laminated state in which flat plates are stacked or toroidally wound. And crystallization treatment, and controlling so that the concentration of Fe is higher than oxygen at a position deeper than 10 nm from the surface and the concentration of Cu is maximized at a position deeper than 5 nm from the surface.
In the present invention, the nanocrystalline alloy is obtained, for example, by producing a Fe-based amorphous alloy containing 3% or less of atomic% of Cu by a single roll method or the like and heat-treating the alloy to a temperature higher than the crystallization temperature. From the viewpoint, it is desirable that the metalloid element be contained at 5% or more in atomic%.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, an important feature of the present invention is that at a position deeper than 10 nm in terms of SiO ₂ from the surface of a thin plate,
That is, the concentration of Fe is higher than that of oxygen, and the concentration of Cu is maximum at a position deeper than 5 nm from the surface. When the thin plate does not satisfy the above conditions when the thin plate is used as a magnetic core, the magnetic permeability of the magnetic core is significantly reduced. In the present invention, the definition of the depth in terms of SiO ₂ is that it is difficult to directly measure the exact depth of an extremely shallow surface, and the sputtering depth of SiO ₂ corresponding to the sputtering time by a photoelectron spectrometer is required. Was evaluated as the actual depth.

It is considered that the reason why the oxygen concentration increases on the surface is that an oxide is formed on the alloy surface. The elements present in the nanocrystalline alloy have different oxidation characteristics. Therefore, when the crystallization treatment is performed in different atmospheres, it is considered that the element concentration distribution of the alloy surface layer differs after the oxide is formed. In particular, in a nanocrystalline alloy, a metalloid element which has a very sensitive effect on magnetic properties is very easily oxidized, and it is presumed that crystallization treatment also fluctuates the concentration distribution of the metalloid element.
When the crystallization treatment is performed in a reduced-pressure atmosphere, elements having a high vapor pressure, such as B, are likely to evaporate from the surface, and the position where the peak of the concentration of Cu is recognized is considered to be a cause of the extreme surface layer.

According to the study of the present inventors, the delicate oxidation state of the pole surface and the difference in the Cu concentration distribution caused by the above-mentioned reasons appear as extremely remarkable changes in the magnetic permeability. This is a critical issue for nanocrystalline alloys.

Specifically, in order to make the surface oxygen concentration and Cu concentration distribution appropriate as specified in the present invention,
For example, a crystallization process is performed by heating an amorphous ribbon capable of expressing a nanocrystal structure with a non-reactive atmosphere gas. Use of a non-reactive gas is effective in suppressing surface oxidation. In addition, it is more effective to prevent elements having a higher vapor pressure from evaporating from the alloy surface than elements constituting the nanocrystalline alloy as compared with the case where a reduced pressure atmosphere is applied. According to the study of the present inventors, when heat treatment is performed with nitrogen gas, a sufficient magnetic permeability is obtained, and it can be treated as a substantially non-reactive gas. Of course, an inert gas can be used as the non-reactive gas, but it is expensive. Hydrogen is not preferable because it reacts with the metalloid element to cause fluctuation in the concentration distribution. Pressure of non-reactive gas atmosphere is atmospheric pressure or higher than atmospheric pressure to suppress the above evaporation from nanocrystalline alloy surface
It is preferable to crystallize at 0.1 to 0.3 MPa (absolute pressure).

The reason why the crystal grain size of the thin plate is set to 100 nm or less is that if the thickness is larger than 100 nm, sufficient magnetic permeability cannot be obtained due to large crystal magnetic anisotropy. Further, Cu increases the number of primary crystal nuclei when heat-treated at a crystallization temperature or higher, and thus has an effect of making crystal grains as a nanocrystalline material fine. The reason why Cu is set to 3% or less in atomic% is that
%, The thin plate becomes brittle. Further, Cu is an element that is easily separated from Fe, so if it is too much, it will be separated from Fe even if the liquid quenching method is used, and it will not be possible to form a solid solution uniformly. . In order to clearly obtain the effect of this element, it is preferable to add 0.1% or more.

The metalloid element in the present invention is C,
It means any of P, Si, B or a compound existing in a composite. This is effective in producing the above-mentioned amorphous alloy, and if it is less than 5%, crystals may be partially formed during the production of the amorphous alloy, which may cause embrittlement.

In the present invention, the magnetic core in which the thin plates are laminated may be obtained by winding an amorphous alloy thin plate in a toroidal shape and heat-treating the amorphous alloy thin plate at a crystallization temperature or higher. Alternatively, the magnetic core formed by laminating at a predetermined height may be heat-treated at a temperature higher than the crystallization temperature, or a punched product may be heat-treated and then laminated. In particular, the toroidal shape is advantageous in that the number of steps is smaller than that obtained by punching and laminating. Also,
The laminated magnetic core is placed in a case made of resin or the like to protect the magnetic core and insulate it from the windings. At this time, the toroidal magnetic core is advantageous in that it is easy to handle because the thin plates are continuously connected.

[0014]

Example: A 1% Cu, Nb 3.0%, Si 15.1%, B6.8% balance molten alloy melt consisting essentially of Fe was quenched by a single roll method, and was amorphous with a width of 27mm and a thickness of 19μm. An alloy sheet was obtained. This amorphous alloy thin plate was wound around an inner diameter of 15 mm and an outer diameter of 19 mm to obtain a toroidal unheated magnetic core. When a ribbon having the above composition and containing 4% of Cu was produced, and a similar magnetic core was produced, it was not possible to produce a magnetic core because it was very brittle. Therefore, using only a 1% Cu amorphous alloy sheet, heat treatment was performed at a temperature higher than the crystallization temperature to analyze the magnetic properties and the surface layer.

The unheated core and a thin plate of the same material
The material cut into mm-square is heat-treated at 525 ° C. (at a crystallization temperature of 508 ° C.) under atmospheric pressure and a nitrogen atmosphere of 0.3 MPa,
These were designated as Invention 1 and Invention 2. Similarly the non-heat-treated core and an atmosphere of a low degree of vacuum in the vacuum degree 14Pa the sample and a vacuum of 1.3 × 10 ^{- 3} in an atmosphere of high vacuum in Pa treated at the same temperature Example compares them respectively 1, Comparative Example And 2.
After the heat treatment, a 10 mm square sample was subjected to analysis of a surface layer by a photoelectron spectrometer. The toroidal magnetic core is placed in a resin case, and the primary and secondary are wound 10 times for both, 800A
The saturation magnetic flux density in a DC magnetic field of / m and the maximum magnetic permeability μm at 50 Hz and 1 kHz were measured.

FIGS. 2, 3 and 4 show the results of analysis by the photoelectron spectrometer of the present invention 1, Comparative Examples 1 and 2. FIG. In addition,
The relationship between the sputtering time and the depth in SiO ₂ of the photoelectron spectrometer used in the present example corresponds to a depth of 3.3 nm per 100 seconds (sec).

In FIG. 2 showing the present invention performed in a nitrogen atmosphere, it can be seen that the concentrations of oxygen and Si in the surface layer are higher than those inside, and conversely, the concentration of Fe is very low. Also,
B and Nb are slightly lower than inside. From these, it is considered that a layer mainly composed of an oxide of Si and Fe is formed. At this time, the atomic concentration of Fe becomes higher than oxygen at a depth of 5 nm or more from the surface. The peak position of the concentration of Cu is at a depth of about 8 nm. That is, the atomic concentration of Fe is higher than oxygen at a position deeper than 10 nm from the surface,
A peak of the atomic concentration of Cu is recognized at a position deeper than 5 nm.

Comparative Example 1 performed in a low vacuum atmosphere
In FIG. 3 which shows that the concentration of Fe, B, and Nb is low, which is considered to be mainly an oxide layer of Si. At this time, it is found that the Fe concentration becomes higher than the oxygen concentration at 11 nm or more, and the region where the oxygen concentration is higher than the Fe concentration is 6 nm deeper than the case where the treatment is performed in nitrogen. The depth of the Cu concentration peak is 14 nm. In FIG. 4 showing Comparative Example 2 performed in a high vacuum atmosphere, the Fe concentration was higher than the oxygen concentration at 2.5 nm or more,
The oxide layer is very thin, but the Cu concentration peak is at a depth of about 2 nm.

Next, Table 1 also shows the measurement results of the photoelectron spectrometer and the measurement results of the saturation magnetic flux density and the maximum magnetic permeability. In the present invention 1 and the present invention 2 in which the atomic concentration of Fe is higher than that of oxygen at a position deeper than 10 nm from the surface and the peak of the atomic concentration of Cu is recognized at a position deeper than 5 nm from the surface, μm is 630000 and 595000, respectively. It showed a very high value, and Bs was 1.2T, which was enough for use in a current transformer. On the other hand, in Comparative Examples 1 and 2 in which the atomic concentration in the surface layer did not satisfy the condition, Bs had the same value, but μm was 135000 and 169000, respectively, which were significantly lower than those of the present invention. . Further, μm at 1 kHz is μm12500 of the present invention 1, the present invention 2, the comparative examples 1 and 2, respectively.
0, μm123000 μm119000, μm121000, the difference is very small, indicating that the present invention is particularly suitable for current transformer applications at several hundred Hz or less.

[0020]

[Table 1]

Further, a wire through which a current of 50 Hz and a current of 0.3 to 3 mA flows was passed through each of the above three types of magnetic cores, each of which was wound with detection winding 100 times, and the output voltage was measured.
Fig. 5 shows the results. Obviously, a high detection voltage was obtained in the present invention heat-treated in nitrogen, confirming the superiority of the current sensor using the laminated magnetic core of the present invention. It was confirmed by a transmission electron microscope that the structure was substantially 100 nm or less in any of the heat treatment atmospheres. Further, even if the treated product in nitrogen is heat-treated in argon instead of nitrogen, μ is almost the same as that in nitrogen.
It was also confirmed that m and output voltage were obtained.

[0022]

The thin plate of the present invention described above is excellent in soft magnetic properties and can be applied to all magnetic applications requiring high magnetic permeability. When applied to a current transformer or the like that requires a particularly high magnetic permeability, the magnetic core obtained by laminating the thin plates can reduce the size of the device and reduce the number of turns of the windings with respect to the magnetic core, and thus have a great industrial value.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a current transformer.

FIG. 2 is a diagram showing an example of a distribution of element concentrations on the surface of a magnetic core according to the present invention.

FIG. 3 is a diagram showing an example of a distribution of element concentrations on the surface of a magnetic core of a comparative example.

FIG. 4 is a diagram showing an example of a distribution of element concentrations on the surface of a magnetic core of a comparative example.

FIG. 5 is a diagram in which a detection voltage is measured assuming the current transformer of the present invention.

[Explanation of symbols]

 1 wire, 2 windings

Claims (5)

[Claims] 1. An Fe-based nanocrystalline alloy containing 3% or less by atomic% of Cu and having a structure of fine crystal grains of 100 nm or less, and at a position deeper than 10 nm from the surface in terms of SiO ₂ ,
A soft magnetic thin plate wherein the atomic concentration of Fe is higher than that of oxygen and the peak of the atomic concentration of Cu is recognized at a position deeper than 5 nm from the surface. 2. The soft magnetic thin plate according to claim 1, wherein the total amount of metalloid elements is 5% or more in atomic%. 3. A magnetic core obtained by laminating the soft magnetic thin plates according to claim 1 or 2. 4. A current transformer using the magnetic core according to claim 3. 5. An atomic percentage of Cu capable of expressing a nanocrystalline structure.
Laminate Fe-based amorphous ribbon containing 3% or less, heat it in a non-reactive gas atmosphere and crystallize it.At a position deeper than 10 nm from the surface in terms of SiO ₂ , the concentration of Fe is higher than oxygen, A method for manufacturing a magnetic core, characterized in that control is performed so that a peak of Cu atomic concentration is recognized at a position deeper than 5 nm.