JPH08176793A - Production of high silicon steel strip by siliconizing treatment method - Google Patents

Abstract

PURPOSE: To produce a high silicon steel strip having a uniform concn. of Si in its transverse direction by a siliconizing treatment method. CONSTITUTION: Slit nozzles formed to <=0.55 in ratio a1 /a2 of the opening area a) of slits and a sectional area a2 in the radial direction of the nozzle pipes of gas flow passages on the inner side of the slits are disposed in a siliconizing treatment furnace at the time of subjecting the stel strip to the siliconizing treatment to penetrate Si therein from its surfaces by disposing the plural slit nozzles apart spaced intervals longitudinally in the siliconizing treatment furnace and spraying treating gases to both surfaces of the steel strip passing in this furnace from the slit nozzles. The treating gases are supplied from the one side ends of the slit nozzles to these nozzles, by which the gas spraying angle θ in positions near the slit ends on the gas supply side is increased and the distribution of the siliconizing quantity in the transverse direction of the strip is made uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high silicon steel strip by a siliconizing treatment method.

[0002]

2. Description of the Related Art As a method for industrially producing a high silicon steel strip having a Si content of 4 wt% or more, JP-A-62-1270.
The siliconizing method shown in No. 78 etc. is known. This manufacturing method introduces heated thin steel strip of Si: less than 4 wt% to a siliconizing treatment furnace, and a process gas containing SiCl ₄ is blown onto the steel strip surface to infiltrate Si into the steel strip, and then,
This is a method for continuously producing a high-silicon steel strip by heat-treating in a diffusion soaking furnace to diffuse Si that has penetrated into the surface of the steel strip in the plate thickness direction. A plurality of slit nozzles are arranged at intervals, and the processing gas is blown onto both surfaces of the steel strip which passes through these slit nozzles.

However, in the siliconizing treatment of the method in which the processing gas is blown from the slit nozzle as described above, due to the flow velocity distribution of the processing gas blown out from the slit nozzle, Si in the steel strip width direction after the siliconizing treatment is caused. There is a problem that the concentration becomes non-uniform. Such non-uniformity of Si concentration in the plate width direction causes a plate shape defect due to a difference in lattice constant due to a difference in Si amount, or causes uneven magnetic characteristics due to a difference in Si amount. In order to solve such a problem, in Japanese Unexamined Patent Publication No. 5-9704, a processing gas is supplied from one side end to slit nozzles arranged at intervals in the furnace length direction and adjacent to each other in the furnace length direction. A method of manufacturing a high silicon steel strip has been proposed in which the processing gas is alternately supplied to the slit nozzles from different end sides so as to make the Si concentration uniform in the plate width direction.

In this manufacturing method, when a slit nozzle of a type that supplies the processing gas from one end is used, the flow velocity distribution of the processing gas blown out from the slit of the nozzle is almost equal to the distribution of the siliconizing amount in the width direction of the steel strip. Paying attention to the coincidence, the processing gas is supplied to the adjacent slit nozzles from different end sides alternately, so that the respective distributions of the siliconizing amounts are superposed to obtain a substantially uniform Si concentration distribution in the plate width direction. It is something to try.

[0005]

However, according to the study by the present inventors, even if the processing gas is supplied to the steel strip surface by the above method, the uniform Si concentration in the plate width direction is not always sufficient. In some cases, it was found that a variation in Si concentration in the plate width direction causes a mountain-shaped concentration distribution that reaches 0.5 wt% or more.

The inventors of the present invention have made extensive studies on a method of eliminating such a Si concentration distribution, and as a result, in order to make the Si concentration uniform in the plate width direction, an appropriate gas blowing angle from the slit nozzle is appropriate. Is important, and this gas blowing angle can be optimized by limiting the ratio of the slit opening area of the slit nozzle to the nozzle pipe radial cross-sectional area of the gas passage inside the slit to a specific range. understood. That is, when the processing gas is supplied to the slit nozzle 1 provided with the slit 2 from one end as shown in FIGS. 1 and 2, the gas outlet angle θ from the slit 2 (gas outlet in the nozzle longitudinal direction). Angle) is smaller than 90 °, and in particular, the gas blowing angle θ at a position near the slit end on the gas supply side becomes extremely small. Then, if the gas blowing angle θ becomes extremely small in this portion, the gas flow velocity on one edge side of the steel strip becomes small, and as a result, the amount of silicidation on the edge side is reduced by the amount on the side of the center of the strip width. Since it is smaller than the amount of silicon, a Si concentration distribution in the plate width direction occurs.

Therefore, by optimizing the gas blowing angle θ from the slit, particularly by increasing the gas blowing angle θ at a position near the slit end on the gas supply side, the Si concentration in the plate width direction is made uniform. be able to.
The gas blowing angle θ depends on the ratio between the slit opening area of the slit nozzle and the nozzle pipe radial cross-sectional area of the gas flow path inside the slit. By optimizing the angle θ, the Si concentration in the plate width direction can be made uniform.

[0008]

The present invention has been made on the basis of such knowledge, and its characteristic constitution is as follows. (1) A plurality of slit nozzles are arranged at intervals in the furnace length direction in the siliconizing furnace, and the processing gas is blown to both sides of the steel strip threaded from the slit nozzles, so that the steel strip is cut from the surface of the steel strip. In a method for continuously producing a high silicon steel strip by performing a siliconizing treatment for infiltrating Si and then performing a heat treatment for diffusing Si in a plate thickness direction in a diffusion soaking furnace, a slit is formed in the siliconizing treatment furnace. Of the opening area a ₁ and the cross-sectional area a ₂ of the gas flow path inside the slit in the radial direction of the nozzle tube
A high silicon steel by a siliconizing method, characterized in that a slit nozzle having a ratio a ₁ / a ₂ of 0.55 or less is arranged and a processing gas is supplied to each slit nozzle from one end thereof. Method of manufacturing obi.

(2) In the manufacturing method of (1) above,
A double-pipe structure having an outer pipe having a slit and a process gas supplied from one end side and an inner pipe opened at the other end side inside the outer pipe, and a nozzle pipe radial cross-sectional area a ₂ of a gas flow path is formed. A method for producing a high silicon steel strip by a siliconizing method, which comprises using a slit nozzle having a gas flow passage cross-sectional area between an inner pipe and an outer pipe. (3) In the manufacturing method according to (1) or (2) above,
A method of manufacturing a high silicon steel strip by a siliconizing method, characterized in that a processing gas is alternately supplied to different slit nozzles or slit nozzle groups adjacent to each other in the furnace length direction from different end sides.

[0010]

The details and reasons for limitation of the present invention will be described below. FIGS. 3 and 4 show an example of the structure of a slit nozzle having a single tube structure arranged in the siliconizing treatment furnace. Such slit nozzles 1 are arranged at intervals in the furnace length direction in the siliconizing treatment furnace. The processing gas is blown to both sides of the steel strip that passes through the slit 2 of each slit nozzle 1 as shown in FIG. 3 and 4, 3 is a gas flow path in the nozzle tube, L is the slit length, W is the slit width, and D is the nozzle tube inner diameter. Therefore, the opening area a ₁ of the slit 2 is a ₁ = L × The cross-sectional area a ₂ of the gas flow path 3 inside the slit in the nozzle tube radial direction due to W is a ₂ = π (D
/ 2) ² respectively.

FIGS. 5 and 6 show an example of the structure of a slit nozzle having a double pipe structure.
Is composed of an outer tube 10 having a slit 2 and an inner tube 11 to which a processing gas is supplied from one end side and the other end side is opened 110 inside the outer tube 10. In the figure, D ₁ is the inner diameter of the outer pipe 10 and D ₂ is the outer diameter of the inner pipe 11. In this case, the gas flow path 3 inside the slit is the inner pipe 11 and the outer pipe 1.
It is a space between 0 and 0. Therefore, in the case of the slit nozzle having the double pipe structure, the opening area a _{1 of the} slit is
Is a ₁ = L × W, and the nozzle tube radial cross-sectional area a ₂ of the gas passage 3 inside the slit is a ₂ = π (D ₁
/ 2) determined respectively by ² - [pi] (D _2/2) ^2.

In the present invention, the area ratio a ₁ / a ₂ between the opening area a ₁ of the slit and the cross-sectional area a ₂ of the gas passage 3 inside the slit in the radial direction of the nozzle tube is set to 0.55 or less. On the other hand, the processing gas is supplied from one end thereof. The gas outlet angle θ from the slit 2 and the gas flow velocity distribution depend on the area ratio a ₁ / a ₂ and this area ratio a
_{When 1} / a ₂ exceeds 0.55, the gas outlet angle θ at the position near the slit end on the gas supply side is less than 80 °, and the gas flow velocity decreases, and the steel strip edge that passes through this part The amount of siliconization in the area is extremely lower than in the central area of the plate width.
In the case of the slit nozzle having the double pipe structure shown in FIGS. 5 and 6, the slit end on the gas supply side means the inner pipe 11
Is the slit end portion on the open end 110 side.

FIG. 7 shows the gas blowing angle θ and the gas flow velocity distribution from the slit 2 and the siliconized amount distribution in the width direction of the steel strip when the area ratio a ₁ / a ₂ exceeds 0.55. In this case, as shown in (a) of the figure, the gas blowing angle θ at a position near the slit end on the gas supply side
Is less than 80 °, the gas flow velocity becomes extremely small in this portion, and the gas flow velocity distribution shown by Xc is obtained. Since the gas flow velocity distribution and the siliconization amount distribution have a substantially proportional relationship, the gas velocity distribution Xc indicates that the siliconization amount distribution in the width direction of the steel strip is Yc.
Becomes ₁ . In addition, FIG.
When the processing gas is supplied from the end portion on the opposite side to the case shown in (1), the distribution of the amount of silicon carbide is Yc ₂ . The above-mentioned JP-A-5
The production method of No. 9704 aims to make such a symmetrical distribution of siliconization amount alternately and to make the distribution of siliconization amount uniform in the plate width direction by superposing these distributions. Even if the distributions of Yc ₁ and Yc _{2 in} (a) are superposed, only the distribution of silicon in which the Si content at the edge portion of the steel strip is low as shown by Zc in FIG.

FIG. 8 shows the gas blowing angle θ from the slit 2 and the gas flow velocity distribution and the siliconized amount distribution in the width direction of the steel strip when the area ratio a ₁ / a ₂ is 0.55 or less. In this case, the gas blowing angle θ is 80 ° or more even at a position close to the slit end on the gas supply side as shown in FIG. 9 (a), and therefore the gas flow velocity is sufficiently high in this part as well, and is therefore indicated by Xi. Such a gas flow velocity distribution is obtained.
Therefore, the distribution of siliconization amount in the width direction of the steel strip is Yi ₁ ,
Further, when the processing gas is supplied to the slit nozzle 1 from the end portion on the side opposite to the case shown in FIG. 8A, the distribution of the siliconizing amount becomes Yi ₂ . Therefore, when the siliconization amount distributions of Yi ₁ and Yi ₂ are superposed according to the manufacturing method of JP-A-5-9704, a uniform siliconization amount distribution in the plate width direction as shown by Zi in FIG. can get.

According to the test results by the present inventors, the area ratio a
_By setting ₁ / a ₂ to 0.55 or less and superimposing symmetrical siliconization amount distributions such as Yi ₁ and Yi ₂ described above, variation in Si amount in the width direction of the steel strip is approximately 0.2 wt% or less. I was able to suppress it. On the other hand, the area ratio a ₁ / a ₂ is 0.7
In the case of, the variation of Si amount in the width direction of the steel strip is 0.5w
It reached over t%. The lower limit of the area ratio a ₁ / a ₂ is not particularly limited, 85 ° if the area ratio a ₁ / a ₂ and 0.1
In order to obtain the above gas blowing angle θ, and to make the area ratio a ₁ / a ₂ less than 0.1, it is necessary to increase the nozzle diameter, resulting in high equipment cost and unnecessary slit nozzle. The area ratio a ₁ / a ₂ is preferably 0.1 or more from the viewpoint of occupying the furnace space.

Further, as shown in FIGS. 5 and 6, the slit nozzle 1 has a double tube structure, so that the variation in the amount of Si in the width direction of the steel strip can be made more uniform. That is, in the slit nozzle 1 having the double pipe structure as shown in FIGS. 5 and 6, the process gas is preheated in the process of passing through the inner pipe 11. Generally, the process gas is preheated outside the furnace to a certain temperature and then supplied into the furnace.
Even if the processing gas preheated outside the furnace is used, the inner pipe 1
In the process of passing 1, the temperature is further raised. And, making the processing gas effective in this way contributes to the uniformity of the amount of Si in the width direction of the steel strip as follows.

First, since the volume of the processing gas increases due to the temperature rise in the inner pipe 11, the apparent gas flow velocity when the gas is blown out from the slit 2 of the slit nozzle 1 increases. Then, as shown in FIG. 13 which will be described later, as the gas flow velocity is higher, the blowing angle θ is stabilized at a higher position, and even in a region where the gas flow velocity is relatively high, it slightly increases but increases in accordance with the increase of the gas flow velocity. The gas outlet angle θ increases. As a result, the slope of the gas flow velocity distribution Xi shown in FIG. 8 becomes smaller, so that the distribution of siliconization amount in the width direction of the steel strip becomes more uniform.

Next, when the temperature of the processing gas blown out from the slit nozzle 1 is relatively low, the reactivity between the processing gas and the steel sheet becomes low. In particular, since the temperature of the edge part of the steel strip tends to decrease, the amount of reaction with the processing gas tends to be smaller than that in the central part of the strip, which also causes uneven distribution of the amount of silicon carbide in the width direction of the strip. It is a factor that spurs. Therefore, in the slit nozzles of FIGS. 5 and 6 capable of sufficiently raising the temperature of the processing gas in the inner pipe 11, since the processing gas having a relatively high temperature can be blown to the steel strip, the steel strip edge It is possible to prevent a decrease in reactivity in the part and make the reactivity uniform in the width direction of the steel strip.

Therefore, due to the above-mentioned two actions, the slit nozzles of FIGS. 5 and 6 have Si in the width direction of the steel strip.
It can be effectively realized by making the amount uniform. Further, since the process gas can be supplied to the furnace while being heated in the inner tube and brought close to the furnace temperature (usually about 1200 ° C.), the asymmetry of convection above and below the steel strip due to the difference in gas density can be eliminated. Can be relaxed.

As described above, the basic operation of the present invention is
By increasing the gas flow velocity at the position near the slit end on the gas supply side, it is intended to improve the extreme decrease in the amount of silicon carbide at the edge of the steel strip. The most rational method of achieving uniform Si concentration in the width direction of the steel strip is to supply the processing gas from different end sides alternately to the slit nozzles or slit nozzle groups adjacent in the furnace length direction. is there.

FIG. 9 shows a case where the processing gas is alternately supplied to the slit nozzles 1 adjacent to each other in the furnace length direction from different end sides, and the symmetrical distribution of the silicidation amount shown in FIG. By the combination, finally, a high silicon steel strip having a uniform Si concentration distribution in the plate width direction can be obtained. Further, FIG. 10 shows a case where the processing gas is alternately supplied to different slit nozzle groups I in the furnace length direction from different end sides,
Even in this case, the high silicon steel strip having a uniform Si concentration distribution in the plate width direction is finally obtained by superimposing the siliconizing amount distributions obtained by the slit nozzle groups I. In addition, 1
The number of slit nozzles forming one slit nozzle group I is arbitrary.

As a method of obtaining a uniform Si concentration distribution in the plate width direction, as shown in FIG. 9 and FIG. 10, different end sides of slit nozzles 1 or slit nozzle groups I adjacent in the furnace length direction are alternately different. Most preferably, the process gas is supplied from The reason for this is that when several slit nozzles with the same process gas supply direction are arranged in series, the degree of Si concentration distribution in the plate width direction cumulatively increases, and plate deformation during the siliconizing process occurs. It is easy to cause But,
When the amount of siliconization per slit nozzle is relatively small, such a problem does not easily occur. Therefore, in the present invention, the slit nozzle 1 or the slit nozzle group I in which the supply direction of the processing gas is different is arranged in the furnace length direction. The case of arranging at random is not excluded. In this case, it is preferable to supply the processing gas from the different end portions of the plurality of slit nozzles 1 or the slit nozzle groups I arranged in the siliconizing treatment furnace from each other. In the present invention, when the slit nozzles 1 are arranged on both sides of the steel strip as shown in FIG. 1, it is possible to supply the processing gas to the pair of slit nozzles from different ends.

[0023]

【Example】

[Embodiment 1] Various slit nozzles having a single-pipe structure as shown in FIGS. 3 and 4 and having different area ratios a ₁ / a ₂ as shown in Table 1 were installed in a siliconizing furnace. 8 slits are arranged at intervals in the direction, and processing gas (SiCl ₄ : 15 mol) is alternately applied to these slit nozzles from different end sides.
%, The balance is substantially N ₂ ) at a supply amount of 5 Nm ³ / h / piece, and a thickness of 0.1 mm and a width of 600 mm of 3% Si.
By subjecting the steel sheet to a siliconizing treatment and then a diffusion heat treatment for diffusing Si in the sheet thickness direction, an average S in the sheet width direction is obtained.
A high silicon steel sheet having an i concentration of 6.5 wt% was manufactured.

Table 1 shows the maximum deviation Si concentration ΔSi in the width direction of the obtained high silicon steel sheet. According to this, when the area ratio a ₁ / a ₂ is 0.55 or less, ΔSi is 0.20.
Area ratio a ₁ / a ₂ while it is suppressed to less than wt%
Is more than 0.55, the amount of Si in the edge portion is extremely small. Particularly, when the area ratio a ₁ / a ₂ is 0.70, ΔSi exceeds 0.5 wt%.

[0025]

[Table 1]

[Embodiment 2] A double pipe structure as shown in FIGS. 5 and 6 and having an area ratio a ₁ / a ₂ as shown in Table ₂
Various slit nozzles with different lengths are arranged in the siliconizing treatment furnace at intervals in the furnace length direction, and the processing gas (SiC
l ₄ : 15 mol%, the balance substantially N ₂ ) is 5 Nm ³ / h
/ Plate thickness 0.1 mm, plate width 60 while supplying at a supply amount of
Silica treatment is applied to 0 mm 3% Si steel plate, and then Si
By performing a diffusion heat treatment to diffuse the in the thickness direction,
A high silicon steel plate having an average Si concentration of 6.5 wt% in the plate width direction was manufactured.

Table 2 shows the maximum deviation Si concentration ΔSi in the width direction of the obtained high silicon steel sheet. Further, FIG. 11 shows the Si concentration distribution in the plate width direction of each high silicon steel plate. In this embodiment, when the area ratio a ₁ / a ₂ is 0.55 or less, ΔSi
Is suppressed to 0.15 wt% or less, whereas when the area ratio a ₁ / a ₂ exceeds 0.55, the amount of Si at the edge portion becomes extremely small, and the area ratio a ₁ / a ₂ is less than 0.1. 68 is ΔSi
Is 0.40 wt%.

[0028]

[Table 2]

[Example 3] Using the same slit nozzle as in Example 2, the gas blowing angle θ was measured at each position in the slit longitudinal direction. The result is shown in FIG. According to the figure, when the sectional area ratio a ₁ / a ₂ is 0.55 or less,
The gas blowing angle θ is 80 ° or more except for a very small portion of the slit end on the gas supply side, and the distribution of the gas blowing angle θ also has a substantially single gradient.
If the range of (1) is set as the steel strip passage portion, a desired distribution of siliconization amount can be obtained. On the other hand, when the cross-sectional area ratio is 0.68, the gas blowing angle θ on the gas supply side is extremely small, and the distribution of the gas blowing angle θ has a two-step gradient. It can be seen that only the distribution of siliconization amount as shown in FIG. 7 can be obtained even for the strip passing portion.

Example 4 The effect of the flow velocity of the gas blown from the slit on the gas blowing angle θ was examined. In this embodiment, a slit nozzle having a double pipe structure as shown in FIGS. 5 and 6 and having an area ratio a ₁ / a ₂ as shown in Table 3 is used, and the flow rate of the gas blown out from the slit is Varying the gas outlet angle θ at a position 100 mm closer to the slit center from the gas supply side slit end
I examined the change of. The result is shown in FIG. According to the figure, if the area ratio a ₁ / a ₂ is 0.55 or less, 0.25
It is understood that the gas blowing angle can be set to 80 ° or more if the gas flow velocity is m / sec or more.

[0031]

[Table 3]

[0032]

According to the present invention described above, when the high silicon steel strip is manufactured by the siliconizing treatment method, the distribution of the siliconizing amount by each slit nozzle can be optimized, and therefore, in the plate width direction. A high silicon steel strip having a uniform Si concentration can be stably manufactured. In addition, since the processing gas is preheated in the process of passing through the inside of the nozzle by adopting the double nozzle structure for the slit nozzle, the preheating temperature of the processing gas outside the furnace can be kept low, and the preheating device can be simplified. You can

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a slit nozzle arranged in a siliconizing treatment furnace.

FIG. 2 is an explanatory view showing a gas blowing direction from a slit of the slit nozzle shown in FIG.

FIG. 3 is a plan view showing one structural example of a slit nozzle having a single pipe structure used for implementing the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a vertical cross-sectional view showing one structural example of a slit nozzle having a double pipe structure used for implementing the present invention.

6 is a sectional view taken along line VI-VI in FIG.

FIG. 7 is an explanatory diagram showing a gas blowing angle θ, a gas flow velocity distribution, and a siliconizing amount distribution when a slit nozzle having an area ratio a ₁ / a ₂ of more than 0.45 is used.

FIG. 8 is an explanatory diagram showing a gas blowing angle θ, a gas flow velocity distribution, and a siliconizing amount distribution when a slit nozzle having an area ratio a ₁ / a ₂ of 0.45 or less is used.

FIG. 9 is an explanatory diagram showing a case where processing gas is alternately supplied to different slit nozzles adjacent to each other in the furnace length direction from different end sides.

FIG. 10 is an explanatory view showing a case where processing gas is alternately supplied from different end sides to adjacent slit nozzle groups in the furnace length direction.

11 is a graph showing the Si concentration distribution in the plate width direction of the high silicon steel strip obtained in Example 2. FIG.

FIG. 12 is a graph showing the gas blowing angle θ at each position in the slit longitudinal direction measured in Example 3

FIG. 13 is a graph showing the relationship between the area ratio a ₁ / a ₂ and the gas flow velocity and the gas blowing angle θ obtained in Example 4.

[Explanation of symbols]

1 ... Slit nozzle, 2 ... Slit, 3 ... Gas flow path, I
... Slit nozzle group 10 ... Outer tube, 11 ... Inner tube, 110 ... Open end

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirohisa Haiji, 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Kazuhisa Okada 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside the Steel Pipe Co., Ltd. (72) Inventor Katsushi Kasai 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (3)

[Claims] 1. A plurality of slit nozzles are arranged at intervals in the furnace length direction in a siliconizing treatment furnace, and a processing gas is blown to both sides of a steel strip threaded through the slit nozzles, thereby forming In a method for continuously producing a high silicon steel strip by performing a siliconizing treatment for infiltrating Si from the surface and then performing a heat treatment for diffusing Si in the plate thickness direction in a diffusion soaking furnace, , Slit opening area a
_A slit nozzle having a ratio a ₁ / a ₂ of ₁ and the radial cross-sectional area a ₂ of the gas flow path inside the slit of 0.55 or less is arranged, and each slit nozzle is processed from one end thereof. A method for producing a high silicon steel strip by a siliconizing method, which comprises supplying gas. 2. A double pipe structure comprising an outer pipe having a slit and a processing gas supplied from one end side and an inner pipe opened at the other end side inside the outer pipe, wherein the gas flow path has a nozzle pipe radial direction. The method for producing a high silicon steel strip by the siliconizing method according to claim 1, wherein a slit nozzle whose cross-sectional area a ₂ is a cross-sectional area of a gas flow path between the inner pipe and the outer pipe is used. 3. The silicidation treatment method according to claim 1, wherein the treatment gas is alternately supplied to different slit nozzles or slit nozzle groups adjacent to each other in the furnace length direction from different end sides. Method for manufacturing high silicon steel strip.