JPH11293414A - High silicon steel plate excellent in high frequency magnetic property and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain stable and excellent high frequency magnetic property by giving the concentration gradient of Si in the plate thickness direction so that the Si concentration at the surface is higher than that at the center part of the plate thickness and specifying the difference between the max. and the min. of the Si concentration in the plate thickness direction, the Si concentration at the surface and the difference between Si concentration at the front surface and at the back surface. SOLUTION: A silicon infiltrating treatment for infiltrating Si from the surface of a steal plate in a non-oxidizing atmosphere containing SiCl4 in the concentration of about 0.02-35 mol.% at about 1023-1250 deg.C and a diffusing treatment for diffusing the infiltrated silicon to the steel plate are carried out at the same time, the respective speeds of silicon infiltration and the diffusion are controlled and the operation is ended in a state that the Si concentration at the surface layer is higher than that at the center part. As a result, the high silicon steel plate having the concentration gradient of Si in the plate thickness direction, having higher Si concentration at the surface than that at the center part and controlled to >=0.3 wt.% in the difference between the max. and the min. of the Si concentration, to 5-7 wt.% in the Si concentration at the surface layer and to <=1 wt.% in the difference between the Si concentration at the front surface and at the back surface and low in iron loss in high frequency is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-silicon steel sheet having excellent high-frequency magnetic properties and used as a core material for transformers and motors, and a method for manufacturing the same.

[0002]

2. Description of the Related Art High silicon steel sheets are used for core materials of transformers and motors. As the Si content increases, the iron loss decreases. %, It is known that the magnetostriction becomes 0 and the magnetic permeability becomes excellent, such as the peak of the maximum magnetic permeability.

Conventionally, as a method for manufacturing a high silicon steel sheet, a so-called siliconizing method has been known in which low silicon steel is made into a thin sheet by rolling, and then Si is diffused from the surface of the steel sheet. However, it takes an extremely long time to produce a high silicon steel sheet having a uniform Si concentration by diffusion. Therefore, Japanese Patent Laid-Open No.
No. 27033 or JP-A-62-227036,
Japanese Patent Publication No. 5-49744 discloses that the Si concentration in the surface layer is 6.5 wt. %, It is proposed that the diffusion process be stopped when the Si concentration distribution exists in the plate thickness direction to shorten the overall processing time. Further, it is shown that the silicon steel sheet having the Si concentration distribution formed in this manner has low iron loss at high frequencies.

As described above, it is effective to form a Si concentration gradient in the thickness direction in order to reduce high-frequency characteristics, particularly, iron loss at high frequencies. In some cases, a desired low iron loss characteristic may not be obtained even if a Si concentration gradient is formed in the thickness direction by using the same.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a silicon steel sheet exhibiting excellent high-frequency magnetic characteristics stably and a method of manufacturing the same.

[0006]

Means for Solving the Problems The present inventors have studied the cause of the case where the high-frequency iron loss does not decrease in the silicon steel sheet having the Si concentration gradient formed as described above.
As a result, it has been found that even if a Si concentration distribution having a high surface Si concentration and a low Si concentration at the center of the plate thickness is formed, the high frequency iron loss does not decrease if the Si concentration difference between the front and back surfaces is large.

[0007] Such a difference in Si concentration between the front and back surfaces occurs because the supply amount of the Si compound gas differs between the front surface and the back surface due to variations in manufacturing conditions when the silicon compound is siliconized by the siliconizing method. And so on.

In order to suppress such a difference in the Si concentration between the front and back surfaces, the warpage of the steel sheet caused by the difference in the Si concentration between the front and back surfaces is measured. It has been found that it is effective to control the amount of the Si compound supplied from the front and back surfaces.

The present invention has been made based on such knowledge, and has a Si concentration gradient in the plate thickness direction, where the Si concentration at the surface is higher than the Si concentration at the center of the plate thickness, Is 0.3 wt. %that's all,
When the Si concentration of the surface layer is 5 to 7 wt. % Of Si on the front and back
The concentration difference is 1 wt. % High-silicon steel sheet having excellent high-frequency magnetic characteristics, which is within 0.1%.

Further, according to the present invention, 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. The diffusion rate is controlled, and while the Si concentration in the surface layer is higher than the Si concentration in the center of the plate thickness, the diffusion is stopped, and the difference between the maximum and minimum Si concentrations in the plate thickness direction is set to 0.
3 wt. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. %, The difference between the Si concentrations on the front and back surfaces is 1 wt. %, And a method for producing a high silicon steel sheet having excellent high-frequency magnetic characteristics, characterized by being within 0.1%.

Further, according to the present invention, the steel sheet is subjected to a siliconizing treatment in a non-oxidizing gas atmosphere containing a Si-based compound, and then a diffusion treatment of Si is carried out in a non-oxidizing gas atmosphere containing no Si-based compound. The diffusion speed is controlled, and while the Si concentration in the surface layer is higher than the Si concentration in the center of the plate thickness, the diffusion is stopped, and the difference between the maximum and minimum Si concentration in the plate thickness direction is set to 0.3 w.
t. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. %, The difference between the Si concentrations on the front and back surfaces is 1 wt. %, And a method for producing a high silicon steel sheet having excellent high-frequency magnetic characteristics, characterized by being within 0.1%.

Further, according to the present invention, in any one of the above methods, the difference in the Si concentration between the front and back surfaces is 1 wt. In order to control the amount of Si compound supplied from the front and back surfaces of the steel sheet, the warp height is measured to be 1% or less of the product width on the exit side of the furnace. To provide a method for producing a high silicon steel sheet having excellent high-frequency magnetic characteristics. Note that it is preferable to use SiCl ₄ as the Si-based compound.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. In the present invention, there is a Si concentration gradient in the thickness direction, the Si concentration on the surface is higher than the Si concentration at the center of the thickness, and the difference between the maximum and minimum Si concentration in the thickness direction is 0.3 watts.
t. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. % Of the high silicon steel sheet, the difference between the Si concentration on the front and back surfaces is 1 wt. %.

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, thereby reducing the apparent thickness. For this purpose, in the present invention, the Si concentration in the surface layer is increased and the Si concentration
Is formed, and the magnetic permeability is increased only in the surface layer portion of the thickness.

However, it has been found that when the difference in Si concentration between the front surface and the back surface is large, the high-frequency iron loss does not decrease. Therefore, in the present invention, the difference between the Si concentration on the front and back surfaces is set to 1 w
t. %. As described above, the difference between the Si concentration on the front and back surfaces is 1 wt. %, A stable high-frequency iron loss can be obtained. Thus, S on the front and back
The reason why the iron loss is reduced when the difference in i concentration is small is presumed to be the stable formation of the high magnetic permeability regions on the front and back and the reduction of the internal strain due to the good shape.

The Si concentration in the surface layer is 5 to 7 wt. % Range. This is because 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. A more preferable range of the Si concentration in the surface layer is 6 to 7 wt. %.

The difference between the maximum and minimum Si concentration in the thickness direction is 0.3 wt. %, The effect of concentrating magnetic flux on the surface layer can be exhibited, and high-frequency iron loss can be effectively reduced.

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

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.

According to the latter method, the structure of the furnace can be simplified by simultaneously performing the siliconizing treatment and the diffusion treatment in the same atmosphere. In addition, the Si concentration distribution can be easily controlled by adjusting the atmosphere in the siliconizing / diffusion treatment furnace, adjusting the introduction point and flow rate of the SiCl ₄ gas, and the moving speed of the steel sheet S,
An extremely flexible process can be performed.

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%.

The Si compound gas is usually supplied from the front side and the back side of the steel sheet. By controlling the supply amount of this gas, the difference in the Si concentration between the front and back surfaces is reduced to 1 wt. %.

However, in the actual operation, it is difficult to measure the Si concentration difference between the front and back surfaces in real time, so that the height of the warp (C warp) in the width direction of the steel sheet is measured on the exit side of the furnace, and the warp is measured. It is preferable to control the amount of the Si compound supplied from the front and back surfaces of the steel sheet so that the height is 1% or less with respect to the product width. In other words, there is a relationship that the greater the Si concentration difference between the front and back surfaces, the greater the warpage of the steel sheet. If the warpage height is 1% or less, the difference in Si concentration between the front and back surfaces is 1%.
wt. %, So that the warp height of the steel sheet is measured on the outlet side of the furnace, and the amount of the Si compound supplied from the front and back surfaces of the steel sheet is feedback-controlled so that the height is 1% or less with respect to the product width. , The difference in Si concentration between the front and back surfaces is 1 wt.
%.

In the present invention, the components other than Si are not particularly limited, and may be any range as long as they are usually 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.

When Mn is contained in a large amount, 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. However, when P is 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, 0.02 w
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.

It should be noted that the Si concentration on the front and back surfaces and the difference between the maximum and the minimum of the Si concentration can be determined from the Si concentration profile obtained by EPMA analysis of the entire plate thickness. Further, the effects of the present invention can be obtained regardless of the thickness of the steel sheet.

[0033]

Embodiments of the present invention will be described below. (Example 1) 3 wt.
% Silicon steel sheet under various conditions by siliconizing.
A high silicon steel sheet having a Si concentration difference of 3% or more was prototyped, and the correlation between the front and back Si concentrations and the iron loss value was investigated.

The temperature of the siliconizing furnace was set to 1200 ° C., and the soaking temperature was set to three zones of 1150 ° C., 1000 ° C. and 900 ° C. The line speed was kept constant at 10 mpm, the flow rate of SiCl ₄ supplied to each of the front and back surfaces was changed, the Si values of the front and back surfaces of the steel sheet were changed, and the iron loss value was measured. Table 1 shows the Si concentration on the front and back surfaces, the Si concentration difference on the front and back surfaces, the average Si concentration difference (ΔSi), and the iron loss value (Epstein measurement value). In addition, it also shows the C-warp height of the steel sheet. The Si concentration at the center of the plate thickness was 3 wt. %
Met. The average ΔSi is a value calculated by the following equation. Average ΔSi = (Surface Si + Back Si) / 2−Center S of Plate
i

[0035]

[Table 1]

As shown in Table 1, those satisfying the present invention obtained low iron loss values according to the surface Si concentration. Further, when the Si concentration of the surface layer is 6.5 wt. % Is uniform 6.5 wt. A lower iron loss value was obtained compared to that of% Si. On the other hand, when the Si concentration in the surface layer deviates or the difference in the Si concentration between the front and back surfaces is 1 wt. % Or more was confirmed to have a high iron loss value. Further, the difference in the Si concentration between the front and back surfaces is 1 wt. %, The C warp height is 1 of the steel plate width.
% Or less.

(Example 2) Thickness 0.1 mm, width 640 m
m 3 wt. % Silicon steel sheet was subjected to siliconizing treatment under various conditions to produce a high silicon steel sheet having a Si concentration difference of 0.3% or more in the thickness direction, and the correlation between the front and back Si concentration and the iron loss value was investigated.

The temperature of the siliconizing furnace was set to 1200 ° C., and the soaking temperature was set to three zones of 1100 ° C., 950 ° C., and 800 ° C. The line speed is constant at 20 mpm,
The iron loss value was measured by changing the flow rate of SiCl ₄ supplied to each of the front and back surfaces, changing the Si values of the front and back surfaces of the steel plate.
Table 2 shows the Si concentration on the front and back surfaces, the difference in Si concentration on the front and back surfaces, and the average S.
The i concentration difference (ΔSi) and iron loss value (Epstein measured value) are shown. In addition, it also shows the C-warp height of the steel sheet. The Si concentration at the center of the plate thickness was 3 to 5 wt. %Met.

[0039]

[Table 2]

As shown in Table 2, those satisfying the present invention obtained low iron loss values according to the surface Si concentration. Further, when the Si concentration of the surface layer is 6.5 wt. % Is uniform 6.5 wt. A lower iron loss value was obtained compared to that of% Si. On the other hand, when the Si concentration in the surface layer deviates or the difference in the Si concentration between the front and back surfaces is 1 wt. % Or more was confirmed to have a high iron loss value. Further, the difference in the Si concentration between the front and back surfaces is 1 wt. %, The C warp height is 1 of the steel plate width.
% Or less.

[0041]

As described above, according to the present invention,
It has a Si concentration gradient in the plate thickness direction, the surface Si concentration is made higher than the Si concentration at the center of the plate thickness, and the difference between the maximum and minimum Si concentration in the plate thickness direction is 0.3 wt. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. %, And the difference between the Si concentrations on the front and back surfaces is set to 1 wt% or less, whereby a silicon steel sheet stably exhibiting excellent high-frequency magnetic characteristics 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 Tsutomu Namikawa 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (5)

[Claims] An Si concentration gradient is present in the thickness direction, the Si concentration at the surface is higher than the Si concentration at the center of the thickness, and the difference between the maximum and minimum Si concentration in the thickness direction is 0.3 wt. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. %, And the difference in Si concentration between the front and back surfaces is 1 wt. % High-silicon steel sheet with excellent high-frequency magnetic properties. 2. A siliconizing treatment for infiltrating Si from the surface of the steel sheet and a 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 stopped, and the difference between the maximum and minimum Si concentration in the plate thickness direction is 0.3 wt. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. %, The difference between the Si concentrations on the front and back surfaces is 1 wt. %. A method for producing a high-silicon steel sheet having excellent high-frequency magnetic characteristics, characterized by being within%. 3. A steel sheet is subjected to a siliconizing treatment in a non-oxidizing gas atmosphere containing a Si-based compound, and then a Si diffusion treatment is carried out in a non-oxidizing gas atmosphere containing no Si-based compound to control the diffusion rate of Si. 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, and the S concentration in the plate thickness direction is reduced.
i is 0.3 wt. % Or more, and the Si concentration of the surface layer is 5 to 7 wt. %, The difference between the Si concentration on the front and back surfaces is 1
wt. %. A method for producing a high-silicon steel sheet having excellent high-frequency magnetic characteristics, characterized by being within%. 4. The method according to claim 2, wherein the difference in Si concentration between the front and back surfaces is 1 wt. In order to control the amount of Si compound supplied from the front and back surfaces of the steel sheet, the warp height is measured to be 1% or less of the product width on the exit side of the furnace. A method for producing a high silicon steel sheet having excellent high frequency magnetic characteristics. 5. The method according to claim 2, wherein SiCl ₄ is used as the Si-based compound.
13. A method for producing a high silicon steel sheet having excellent high-frequency magnetic characteristics according to the above item.