JPH11293415A - Iron core low in residual magnetic flux density and excellent in workability and high frequency characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an iron core composed of a high silicon steel sheet, low in residual density and excellent in workability while maintaining excellent high frequency characteristics. SOLUTION: By a high silicon steel sheet having an Si concn. gradient in which the concn. Si in the outermost surface layer is regulated to 5 to 7 wt.%, the thickness of a high Si concn. layer formed on the surface layer part and in which the concn. of Si is regulated to >=3.5 wt.% is regulated to <=25% of the whole body of the sheet thickness, and the difference between the maximum and the minimum of the Si concn. is regulated to >=0.3 wt.% in the sheet thickness direction, an iron core low in residual magnetic flux density and excellent in workability and high frequency characteristics is composed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer, a reactor, and a transformer (CT) in which an inrush current due to magnetic bias is a problem.
The present invention relates to an iron core made of a high silicon steel sheet used for motors and motors. Examples of such an iron core include a cut core, an EI, and a cut core.

[0002]

2. Description of the Related Art A high silicon steel sheet is frequently used for an iron core of a transformer, a motor, and the like because of its excellent high-frequency magnetic characteristics such as low iron loss and high magnetic permeability. In particular, Si: 6.
5 wt. %, It is known that the magnetostriction becomes 0 and exhibits more excellent high-frequency magnetic characteristics such as the peak of the maximum magnetic permeability.

Hitherto, as a method for producing such a high silicon steel sheet, a so-called siliconizing method has been known in which low silicon steel is formed into a thin sheet by rolling, and then Si is diffused from the surface of the steel sheet. However, such high silicon steel sheet is a brittle material,
There is a problem that a break occurs when the steel sheet is wound up after the treatment.

On the other hand, Japanese Patent Application Laid-Open No. 62-227033 discloses
From JP-A-62-227036 and JP-A-4-246157, it is disclosed that workability is improved by forming a Si concentration gradient in the thickness direction of the sheet. However, in these publications, the basis of workability is 6.5 wt. % Silicon steel sheet,
With these technologies, 6.5 wt. Although the workability is better than that of a% silicon steel sheet, it cannot be said that sufficient workability has been obtained. That is, by these techniques, the Si
When the concentration is reduced, the total thickness becomes 6.5 wt. The workability is improved as compared with the steel sheet of% Si, but when subjected to severe processing, inconveniences such as cracks occur.

On the other hand, silicon steel sheets have been studied to increase magnetic flux density and reduce iron loss in order to obtain good magnetic properties, and materials having a large squareness ratio have been developed. But,
As a result, the residual magnetic flux density increases, and in the case of a device such as a transformer, various problems occur due to the magnetic polarization.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is an iron core made of a high-silicon steel sheet, having a low residual density and excellent workability while maintaining excellent high-frequency characteristics. The purpose is to provide.

[0007]

Means for Solving the Problems The present inventors have conducted various studies to obtain a core having high magnetic properties and excellent workability using a high silicon steel sheet. It has been found that it is effective to define the concentration gradient in a specific range and make the ratio of the high Si concentration layer in the surface layer portion to the total plate thickness in the specific range effective.

The present invention has been made based on such findings, and the Si concentration in the outermost layer is 5 to 7 wt. %, 3.5 wt.% Of Si formed on the surface layer. %
The thickness of the concentration layer is 25% or less of the entire thickness, and the difference between the maximum and the minimum of the Si concentration is 0.3 wt. An iron core having a low residual magnetic flux density and excellent in workability and high-frequency characteristics, characterized by being made of a high silicon steel sheet having a Si concentration gradient of not less than%.

Further, according to the present invention, the Si concentration in the outermost layer is 5 to 5.
7 wt. %, 3.5 wt.% Of Si formed on the surface layer. %
The thickness of the high Si concentration layer described above is 20% or less of the entire plate thickness, and the Si concentration at the center of the plate thickness is 3 wt. % Or less, comprising a high silicon steel sheet having a Si concentration gradient in the sheet thickness direction and having a low residual magnetic flux density and excellent in workability and high-frequency characteristics.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. In the present invention, the Si concentration in the outermost layer is 5-7.
wt. %, And 3.5 wt. %, The thickness of the high Si concentration layer is 25% or less of the entire plate thickness, and the difference between the maximum and the minimum of the Si concentration is 0.3 wt. % Of the iron core is made of a high silicon steel sheet having a Si concentration gradient of not less than%.

In order to reduce iron loss at a high frequency of 5 kHz or more, it is effective to increase the magnetic permeability only in the vicinity of the surface layer of the steel sheet and to concentrate the magnetic flux there to reduce the apparent thickness. Therefore, in the present invention, the Si concentration in the surface layer is set to 5 to
7 wt. %, The Si concentration at the center of the plate thickness is lowered, a concentration gradient of Si is formed in the plate thickness direction, and the magnetic permeability is increased only in the surface layer portion of the plate thickness. When the surface Si concentration is 5 wt. % And 7 wt. %, The effect of increasing the magnetic permeability near the surface layer of the steel sheet as described above is low. Also, 7
wt. %, The workability deteriorates. Surface S
The more preferable range of the i concentration is 6 to 7 wt. %.

The residual magnetic flux density strongly depends on the difference (ΔSi) between the maximum and the minimum of the Si concentration in the thickness direction, and as this value increases, the absolute value decreases. This is presumed to be because the lattice constant decreases with the addition of Si, and a tension is generated in the steel sheet by forming a Si concentration gradient.

In the present invention, from the viewpoint of reducing the high-frequency iron loss as described above and the viewpoint of reducing the residual magnetic flux density,
ΔSi in the thickness direction is 0.3 wt. % Or more.

Further, according to the present invention, in order to maintain the residual magnetic flux density and the high-frequency iron loss at a low level and to improve the workability as described above, in addition to the above-mentioned rules, the amount of Si formed on the surface layer is 3%. .5 wt. %, The thickness of the high Si concentration layer is 25% or less of the entire plate thickness. This is because if the high Si concentration layer in the surface layer portion is too thick, it becomes a brittle material and tends to crack due to stress concentration. The definition of 25% or less is a ratio of the thickness of the high Si layer on one surface to the total thickness.

By satisfying the above conditions, it is possible to obtain an iron core capable of withstanding severe processing such as caulking press while maintaining low residual magnetic flux density and high-frequency iron loss.

The Si concentration in the outermost layer is 5 to 7 wt.
%, 3.5 wt.% Of Si formed on the surface layer. % Or more of the high Si concentration layer is 20% or less of the entire plate thickness,
The Si concentration at the center of the plate thickness is 3 wt. % Or less
It is more preferable to have a concentration gradient of i. By satisfying such conditions, particularly good workability can be obtained while maintaining low residual magnetic flux density and high-frequency iron loss, and swaging can be performed well.

The silicon steel sheet having a concentration gradient of Si constituting the iron core of the present invention can be produced by, for example, a chemical vapor deposition (CVD, siliconizing treatment) method, a physical vapor deposition (PVD) method, a clad technique, a plating technique, or the like. Although it is possible to manufacture by these methods, it is preferable to manufacture by these methods among them.

In the CVD method, a steel sheet is subjected to a siliconizing treatment in a non-oxidizing gas atmosphere containing a Si-based compound.
By performing a diffusion process of Si in a non-oxidizing gas atmosphere containing no system compound to control the diffusion rate of Si, by cutting off while the Si concentration in the surface layer is higher than the Si concentration in the center of the plate thickness, The above-described Si concentration distribution can be formed.

The siliconizing treatment for infiltrating Si from the surface of the steel sheet and the diffusion treatment for diffusing the infiltrated Si into the steel sheet are simultaneously performed in a non-oxidizing atmosphere containing a Si compound to control the siliconizing and diffusion rate. Then, while the Si concentration in the surface layer is higher than the Si concentration in the center of the plate thickness, the cutting is performed.
The above-described Si concentration distribution can also be formed.

Here, the siliconizing treatment is performed using a Si compound gas. The Si compound gas used for the treatment is not particularly limited, and SiH ₄ , Si ₂ H ₅ , SiCl _{4 and the} like can be used, and among them, SiCl ₄ is preferable.
When SiCl ₄ is used as the processing gas, it is preferable that the processing temperature be in the range of 1023 to 1250 ° C.
Further, the concentration of SiCl ₄ during the siliconizing treatment and the diffusion treatment is preferably set to 0.02 to 35 mol%.

In the present invention, the components other than Si are not particularly limited, and may be any range as long as they are generally used as this type of steel sheet. That is, C ≦ 0.02 wt.
%, 0.05 wt. % ≦ Mn ≦ 0.5 wt. %, P ≦
0.01 wt. %, S ≦ 0.02 wt. %, 0.001
wt. % ≦ sol. Al ≦ 0.06 wt. %, N ≦ 0.
01 wt. % Is preferred.

If C is contained in a large amount, it causes magnetic aging. % Is preferable. Although there is no particular lower limit in terms of characteristics, 0.001 wt. % Is preferable.

If a large amount of Mn is contained, the steel sheet becomes brittle. % Is preferable. On the other hand, if the content is too low, breakage and surface flaws are induced in the hot rolling step. % Is preferable.

P is a preferable element from the viewpoint of magnetic properties, but if contained in a large amount, the workability of the steel sheet is deteriorated. % Is preferable. Although there is no particular lower limit in terms of characteristics, 0.001 wt. % Is preferable.

Since S deteriorates workability, 0.02w
t. % Is preferable. Although there is no particular lower limit on the characteristics, from the viewpoint of economical removal, 0.0 is preferred.
01 wt. % Is preferable.

Sol. Al also impairs workability, so 0.06 wt. % Is preferable. On the other hand, 0.001 wt. %
The above is preferred.

If N is contained in a large amount, it forms nitrides and deteriorates magnetic properties. % Is preferable. Although there is no particular lower limit in terms of characteristics, 0.0001 wt. % Is effectively the lower limit.

The Si concentration in the surface layer, the difference between the maximum and the minimum of the Si concentration, the thickness of the high Si concentration layer, and the Si concentration in the central portion are determined from the Si concentration profile obtained by EPMA analysis of the entire plate thickness. be able to. Further, the residual magnetic flux density is a value after 1.2T excitation with direct current. Furthermore, the effects of the present invention can be obtained regardless of the thickness of the steel sheet.

[0029]

Embodiments of the present invention will be described below. 3 wt. % Silicon steel sheet under various conditions to change the Si concentration in the surface layer, the thickness ratio on one side of the high Si concentration layer in the surface layer, and the ΔSi value.
The relationship between high frequency iron loss and residual density was investigated. Table 1 shows the results.

In Table 1, the pressability was evaluated by the number of presses until the burr exceeded 30 μm in a round hole continuous press with a carbide blade. The evaluation criteria were 50,000 or less: ×, 5 to 15
10,000 times: Δ, 15-250,000 times: 、, 250,000 times or more: ◎. As for the bending workability, 90 ° bending and 180 ° bending were performed assuming that a substantially right-angled bending was formed during the production of the cut core. The evaluation at this time was as follows: cracking: X, cracking:
、, no cracks / cracks: ◎.

[0031]

[Table 1]

As shown in Table 1, when the surface layer Si, the thickness of the Si layer, and ΔSi were within the ranges of the present invention, the high-frequency iron loss and the residual magnetic flux density were low, and the workability was good.
In particular, when the Si concentration is 5 to 7 wt. %, The thickness of the high Si concentration layer is 20% or less of the entire thickness, and the Si concentration at the center of the thickness is 3w.
t. % Or less, the pressability was ◎, and caulking press such as V caulking was possible.

[0033]

As described above, according to the present invention,
By using a silicon steel sheet that defines the surface Si concentration, the Si concentration gradient in the plate thickness direction, and the thickness of the high Si concentration layer in the surface layer portion, the residual density is low, and workability is maintained while maintaining excellent high-frequency characteristics. Excellent iron core can be obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshikazu Takada 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Tatsuhiko Hiratani 1-1-1, Marunouchi, Chiyoda-ku, Tokyo No. 2 Inside Nihon Kokan Co., Ltd.

Claims (2)

[Claims] 1. The method according to claim 1, wherein the outermost layer has a Si concentration of 5 to 7 wt. %, 3.5 wt.% Of Si formed on the surface layer. %
The thickness of the i-concentration layer is 25% or less of the entire plate thickness, and the difference between the maximum and the minimum of the Si concentration is 0.3 wt. An iron core having a low residual magnetic flux density and excellent in workability and high-frequency characteristics, which is made of a high silicon steel sheet having a Si concentration gradient of not less than%. 2. The method according to claim 1, wherein the outermost layer has a Si concentration of 5 to 7 wt. %, 3.5 wt.% Of Si formed on the surface layer. %
The thickness of the i-concentration layer is 20% or less of the entire plate thickness, and the Si concentration at the center of the plate thickness is 3 wt. % Or less in the thickness direction.
An iron core having a low residual magnetic flux density and excellent in workability and high frequency characteristics, which is made of a high silicon steel sheet having an i concentration gradient.