JP3045009B2 - Silicon steel strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon steel strip manufactured by a continuous gas siliconizing method.

2. Description of the Related Art Japanese Patent Application Laid-Open No. 62-2270 discloses a method for industrially producing a high silicon steel strip having a Si content of 4 wt% or more.
No. 78, etc., is known as a gas-silicon production method. In this production method, a thin steel strip of less than 4 wt% of Si is continuously passed through a siliconizing furnace in an atmosphere containing SiCl ₄ to infiltrate the steel strip with Si and then diffuse Si in the thickness direction. This is a method for continuously producing coiled high silicon steel strip by performing heat treatment. According to this manufacturing method, it is possible to manufacture a so-called 6.5% Si steel strip having excellent magnetic properties. There is a problem that the steel strip is easily broken or edge cracked during the passing of the steel strip.

[0002]

A silicon steel strip having an Si content of 5 wt% or more is very brittle. In particular, when a steel strip having a Si content of more than 6.3 wt% is passed through a continuous processing line, the steel strip is not brittle. Cracking (edge cracking) proceeds from the edge portion with only a slight bending or twisting, and easily breaks. To prevent bending and twisting of the steel strip, increase the roll diameter of the steering roll and bridle roll of the line as much as possible.Prevent meandering of the steel strip in the furnace and cause bending and twisting of the steel strip. From the viewpoint of reducing opportunities, measures such as shortening the furnace length of the continuous processing furnace can be considered.However, regarding the increase in the diameter of the roll, there is a Even if the steel strip is twisted, the plate will break.
Also, increasing the diameter of the roll is not preferable from the viewpoint of equipment cost. In addition, since it is necessary to reduce the line speed in order to secure a desired siliconized amount, there is a great disadvantage that productivity is reduced.

[0003] Further, in the silicon strip treatment of the steel strip in the continuous line, since the restraining force of the steel strip edge is smaller than that of the steel strip center, the steel strip is likely to be warped due to the contraction of the steel strip during the siliconization reaction. As shown in FIG. 8, a plate shape defect in which an edge portion is turned up easily occurs. And such a plate shape defect is S
i: If it occurs in a steel strip of 6.3 wt% or more, edge cracks will occur in the steel strip during the passage of the roll portion. As described above, the high silicon steel strip manufactured by the conventional gas silicification processing line is liable to cause breakage and edge cracking during threading, which makes continuous production difficult and low productivity. was there.

[0004]

In view of such conventional problems, the present inventors have studied a structure of a silicon steel strip manufactured by a gas-siliconized method that does not cause breakage or edge cracking during manufacturing. As a result of performing the above, the silicon steel strip to be manufactured is provided with a Si concentration distribution in the plate width direction, specifically, by reducing the Si content in the edge portion as compared with the central portion in the plate width direction, the above-described problem is solved. We found that we could avoid it properly. Conventionally, in the gas siliconizing method, a natural goal is to obtain a high silicon steel strip having a uniform Si concentration in the sheet width direction.
For example, in Japanese Patent Application Laid-Open No. 5-9704, S in the plate width direction generated by using a slit nozzle
From the viewpoint of preventing variation in the i concentration and making the Si concentration in the plate width direction as uniform as possible, there has been proposed a method for supplying a reactive gas to a slit nozzle. However, according to the study of the present inventors, a high silicon steel strip having a uniform Si concentration in the sheet width direction is liable to cause the above-described edge cracking and sheet breakage. It has been found that the high silicon steel strip having a reduced Si content in the portion hardly causes edge cracking and breakage. The present invention has been made based on such knowledge, and the characteristic configuration thereof is as follows.

(1) A silicon steel strip manufactured by a continuous gas siliconizing method, wherein a Si content [% Si (C)] (wt%) in a central portion in a plate width direction and a Si content in an edge portion in a plate width direction. Content [% Si (E)] (wt%) and [% Si (C)]
> A silicon steel strip satisfying the relationship of [% Si (E)].

(2 ) In the silicon steel strip of the above (1) ,
[% Si (C)]: 6.3 to 8 wt%, [% Si (E)]:
Silicon steel strip with less than 6.3 wt%.

[0007]

FIG. 9 shows the relationship between the Si content of the silicon steel sheet and the mechanical properties. As shown in the figure, the elongation of the silicon steel sheet decreases as the Si content increases, and when the Si content exceeds 5 wt%, the elongation becomes almost zero and becomes very brittle. Table 1 shows the critical bending radius according to the thickness of the 6.5% Si steel sheet. It can be seen that the critical bending radius of the 6.5% Si steel sheet is very large. For this reason, the 6.5% Si steel strip is slightly bent or twisted in the threading of the line, and cracks easily occur when locally bent at a curvature larger than the critical bending radius. In particular, since bending and twisting are likely to occur at the edge, cracks enter from the edge and break the plate in most cases. Therefore, in order to prevent the plate from breaking, it is necessary to prevent the occurrence of cracks (edge cracks) at the edges.

In the present invention, the Si content [% Si (E)] at the edge portion in the plate width direction of the silicon steel strip is made lower than the Si content [% Si (C)] at the center portion in the plate width direction. In addition, the occurrence of cracks at the edge portion is prevented, and as a result, breakage of the plate during passing is prevented. FIG. 1 shows the pattern of the Si concentration distribution in the width direction of the silicon steel strip of the present invention. The Si concentration distribution in the plate width direction may be either a smooth mountain-like distribution as shown in FIG. 3A or a steep distribution as shown in FIG. 3B, but in consideration of the product yield ( The distribution shown in b) is more preferable. In the present invention, the Si content of the silicon steel strip is not particularly limited, but cracks easily occur when the Si content is 5 wt% or more. Therefore, the present invention is particularly applied to a silicon steel strip having a Si content of 5 wt% or more. It is valid.

[0009] The Si content is made lower than the central part in the sheet width direction.
That the range of the plate width direction edge portions satisfy the following conditions
It is preferred to add. In the case where the steel strip width is less than 300 mm, the width of the steel strip width in the strip width direction including a portion of 15% or more of the steel strip width in the strip width direction from each edge of the steel strip is 300 m.
m or more, 50 m from each edge of the steel strip in the sheet width direction
When the range of the plate width direction edge portions should be as low a plate width direction edge portion Si content including more portions m is less than the width defining in above, the frequency of cracks at the edge portion is higher plate breaking Tends to occur.

Further, Si: 6.3 to 8 wt% of a high silicon steel strip (that is, a Si content [% Si
(C)] is 6.3 to 8 wt% high silicon steel strip),
The Si content [% Si (E)] of the edge portion in the width direction of the sheet was adjusted to 6.3.
It is preferable to set the range of the edge portion in the plate width direction to be less than wt% and to restrict the Si content as described above. As described above, the silicon steel strip has a Si content of 6.3.
% or more, it becomes extremely brittle.
(C)]> [% Si (E)], when [% Si (E)] is 6.3 wt% or more, cracks are likely to occur at the edge portion.

Next, a method for producing a silicon steel strip according to the present invention will be described. FIG. 2 shows an example of a continuous production line for high silicon steel strip by the gas siliconizing method. In this production line, the raw steel strip S unwound from the payoff reel 1 (for example,
The 3% Si steel strip) passes through the cleaning equipment 2, is heated to or near the siliconizing treatment temperature in the heating zone 3 in a non-oxidizing atmosphere, and is then introduced into the siliconizing treatment zone 4. As shown in FIG. 3, spray nozzles 10 are arranged in the siliconized zone 4 at intervals in the furnace length direction.
The processing gas containing SiCl ₄ as a reaction gas from the steel strip S
Of the steel strip S, the SiCl ₄ reacts with Fe in the steel strip, thereby enriching the surface layer of the steel strip S with Si. Next, the steel strip S is guided to the diffusion layer 5, subjected to a diffusion heat treatment for diffusing Si in the thickness direction in a non-oxidizing atmosphere containing no SiCl ₄ , and cooled in the cooling zone 6. 7 and the oven 8 coated with an insulating film,
It is wound on a tension reel 9 as a product steel strip (for example, a 6.5% Si steel strip). The spray nozzle 10 arranged in the siliconized zone 4 is constituted by a slit nozzle having a slit 11 as shown in FIG. 4, and is arranged parallel to the width direction of the steel strip S passing through the slit nozzle. is there.

The silicon steel strip of the present invention is, for example, shown in FIG.
(A) Those having the Si concentration distribution can be manufactured by making the width of the slit 11 of the spray nozzle 10 smaller than the plate width. Also, S in FIG.
For those having the i concentration distribution, the width of the slit 11 of the spray nozzle 10 is slightly larger than the width of the steel strip, and the position of the slit 11 in the width direction of the steel strip is alternately shifted for each adjacent nozzle. It can be manufactured by adjusting the gas flow blown to the steel strip.

[0013]

[Table 1]

[0014]

【Example】

Example 1 In a continuous production line for high silicon steel strips shown in FIGS. 2 to 4, 6.5% Si steel strips having a thickness of 0.3 mm, a width of 400 mm and a width of 600 mm were used as 3% Si steel strips.
A steel strip was manufactured. In this embodiment, the nozzle slit width (see FIG. 4) of the spray nozzle 10 is set to 1.1 to 1.1 with respect to the steel strip width.
A 6.5% silicon steel strip having a different Si concentration distribution in the sheet width direction is produced by alternately shifting the position of the nozzle slit in the sheet width direction for each of the adjacent nozzles while setting the range to 1.3 times. Then, the occurrence of cracks and plate breakage was examined. The results are shown in Table 2, and the Si concentration distribution in the sheet width direction of each high silicon steel strip is shown in FIG. 5 (sheet width: 600 mm) and FIG.
mm).

[0015]

[Table 2]

[Embodiment 2] A high silicon steel strip shown in FIGS.
A 6.5% Si steel strip was manufactured from a 0% 3% Si steel strip. In this embodiment, the nozzle slit width of the spray nozzle 10 is set in a range of 1.0 to 1.3 times the width of the steel strip, and the position of the nozzle slit in the width direction of the steel strip is alternately set for each adjacent nozzle. In this way, 6.5% silicon steel strips having different Si concentration distributions in the sheet width direction were manufactured, and the occurrence of cracks and sheet breaks were examined. Table 3 shows the results, and FIG. 7 shows the Si concentration distribution in the width direction of each high silicon steel strip.

[0017]

[Table 3]

[0018]

As described above, the silicon steel strip of the present invention
There is no occurrence of edge cracking or plate breakage during production, and stable production with high productivity is possible.

[Brief description of the drawings]

FIG. 1 is a drawing showing a Si concentration distribution pattern in a sheet width direction of a silicon steel strip of the present invention.

FIG. 2 is an explanatory view showing a continuous production line for high silicon steel strip by the gas siliconizing method.

FIG. 3 is an explanatory view showing a state of gas blowing from a blowing nozzle in a siliconizing zone of the production line shown in FIG. 2;

FIG. 4 is an explanatory view showing the spray nozzle of FIG. 3;

FIG. 5 shows a silicon steel strip (plate width 600 m) obtained in Example 1.
m) Graph showing the Si concentration distribution in the sheet width direction of FIG.

FIG. 6 shows a silicon steel strip (plate width 400 m) obtained in Example 1.
m) Graph showing the Si concentration distribution in the sheet width direction of FIG.

FIG. 7 shows a silicon steel strip obtained in Example 2 (having a sheet width of 280 m).
m) Graph showing the Si concentration distribution in the sheet width direction of FIG.

FIG. 8 is an explanatory view showing a plate shape defect occurring in the conventional siliconizing treatment.

FIG. 9 is a graph showing the relationship between the Si content of silicon steel sheets and mechanical properties.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pay-off reel, 2 ... Cleaning equipment, 3 ... Heating zone, 4 ... Siliconized zone, 5 ... Diffusion uniform zone, 6 ... Cooling zone, 7
... Insulation coating coater, 8 ... Oven, 9 ... Tension reel, 10 ... Spray nozzle, 11 ... Slit, S ... Steel strip

Continued on the front page (72) Inventor Morihiro Wada 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Hirohisa Kashi 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Katsushi Kasai 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 10/06-10/16 C23C 16 / 24,16 / 54

Claims (2)

(57) [Claims] 1. A silicon steel strip manufactured by a continuous gas siliconizing method, wherein a Si content [% S
i (C)] (wt%) and the Si content [% Si (E)] (wt%) at the edge portion in the width direction of the sheet are [% Si (C)]> [%
Si (E)]. 2. % Si (C): 6.3 to 8 wt%,
The silicon steel strip according to claim 1 , wherein [% Si (E)] is less than 6.3 wt%.