JP3183129B2 - Method for producing high silicon steel sheet with excellent surface properties - Google Patents

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 sheet by a siliconizing treatment method.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 62-2270 discloses a method for industrially producing a high silicon steel sheet having a Si content of 4 wt% or more.
No. 78 is known. In this manufacturing method, a thin steel sheet containing less than 4 wt%
₄ is a method of obtaining a high silicon steel sheet by infiltrating Si by reacting with Si at a high temperature and diffusing the infiltrated Si in the thickness direction.
In Japanese Unexamined Patent Application Publication No. 62-26324, a steel sheet is continuously siliconized at a temperature of 1023 ° C. to 1200 ° C. in a non-oxidizing atmosphere containing ₅ to 35 wt% of SiCl ₄ to form a coil. High silicon steel sheet is obtained.

Generally, in the siliconizing treatment of a steel sheet, SiCl ₄ is used as a raw material gas for supplying Si, and the SiCl ₄ reacts with the steel sheet according to the following reaction formula and Si penetrates into the surface layer of the steel sheet. SiCl ₄ + 5Fe → Fe ₃ Si + 2FeCl _{2 In} this manner, the Si that has permeated the steel sheet surface layer is SiCl ₄
The steel sheet is diffused in the thickness direction by soaking in a non-oxidizing gas atmosphere containing no.

[0004] In order to continuously siliconize a steel sheet by such a process, a continuous siliconizing line as shown in FIG. 3 is used. The continuous siliconizing line has a heating zone, a siliconizing zone, a diffusion zone and a cooling zone from the inlet side. After the steel sheet is continuously heated to the processing temperature in the heating zone, it reacts with SiCl _{4 in the} siliconizing zone. The Si
Then, a heat treatment for continuously diffusing Si in the thickness direction in the diffusion layer is performed, and then cooled in a cooling zone to produce a coil-shaped high silicon steel sheet.

[0005]

However, when a high silicon steel sheet is manufactured by the above-described continuous siliconizing line, there is a problem that a steel sheet being manufactured has a pressing flaw and the quality of a product steel sheet is impaired. . The present inventors have repeatedly studied the cause of such a problem, and as a result, silica generated by the reaction of SiCl ₄ with a trace amount of oxygen or moisture in the atmosphere in the siliconized zone causes press flaws on the steel sheet. I found out that he was the culprit. It has also been found that the silica adheres to the steel sheet in the form of powder or thin film, thereby deteriorating the adhesion of the insulating film.

[0006] That is, a large amount of reactive gas SiCl ₄ is supplied to the siliconized zone for infiltrating Si, but since SiCl ₄ is a very active gas, it reacts directly with the steel sheet. Then, it reacts with a trace amount of oxygen or moisture in the furnace atmosphere as shown in the following formula to produce silica (SiO ₂ ). SiCl ₄ + O ₂ → SiO ₂ + 2Cl ₂ SiCl ₄ + 2H ₂ O → SiO ₂ + 4HCl

The silica is formed in the gas phase or on the surface of the steel sheet by the above-mentioned reaction and adheres to the steel sheet in a powdery or thin film state. The silica powder attached to the lower surface of the steel sheet is used for conveying the steel sheet provided in the furnace. Attaches to the surface of the hearth roll. And
It was found that the adhesion of the silica powder caused irregularities on the surface of the hearth roll, and the irregularities caused press flaws on the steel sheet heated to a high temperature (this phenomenon was called pickup). In addition, the silica powder generated in the gas phase adheres and accumulates on the surface of the refractory inside the furnace and contaminates the inside of the furnace,
Silica powder adhering to the surface of the refractory falls onto the steel plate or hearth roll, causing scratches on the steel plate.Furthermore, powdery or thin silica adhering to the surface of the steel plate degrades the adhesion of the insulating film. It turned out that it was. Therefore,
As a measure to suppress the generation of such silica, it is conceivable to perform atmosphere control such that the oxygen concentration and the dew point in the atmosphere in the siliconized zone are reduced as much as possible.

In a general continuous annealing line, in order to suppress the oxidation of the steel sheet surface, the operation is performed while maintaining the oxygen concentration and the dew point (water vapor concentration) in the furnace at a certain level or less.
Regarding the atmosphere in the furnace of the continuous siliconizing treatment line, for example,
Japanese Patent Application Laid-Open No. 6-212397 has a problem that when siliconizing treatment is performed in an atmosphere having a water vapor concentration corresponding to a dew point of −30 ° C. or higher, the steel sheet surface and crystal grain boundaries are oxidized, and the bending workability of the product is deteriorated. For this reason, the publication discloses that the oxidation of the steel sheet surface and the crystal grain boundaries is prevented and the oxygen concentration in the furnace atmosphere is 45 p.
pm or less, dew point of -30 ° C or less, and oxygen concentration [O ₂ ]
(Ppm) and water vapor concentration [H ₂ O] (ppm) have been proposed to control the furnace atmosphere so as to satisfy the conditions of the following equation.

(Equation 1) However, since the inside of the siliconized zone of the continuous siliconizing treatment line is a special environment in which the above-described siliconizing reaction occurs, it is much more difficult to control the furnace atmosphere as compared with a general continuous annealing line or the like.

In particular, recently, the use ratio of fiber-based refractories having excellent heat insulating properties as a furnace refractory has been increasing, and since the fiber-based refractories have a high porosity, H ₂ O is used.
In addition, when the furnace is opened to the atmosphere immediately after construction of the furnace or at the time of furnace repair or inspection, a large amount of air or moisture is absorbed therein. Therefore, the moisture and air absorbed in such a refractory gradually leaches into the furnace atmosphere during operation, and therefore, it is extremely difficult to control the atmosphere in the siliconized zone. Therefore, it is not easy to control the atmosphere in the furnace as disclosed in Japanese Patent Application Laid-Open No. 6-212397.
Even if such a low dew point and low oxygen concentration can be realized in the early stage of the furnace operation, if the operation is continued for a certain period of time, the dew point and the oxygen concentration increase, and pickup occurs.

[0010] Accordingly, an object of the present invention is to suppress the generation of silica in a siliconized zone even when the dew point and the oxygen concentration of the atmosphere in the furnace of the siliconized zone are relatively high, and to provide a pickup caused by the silica generation. It is an object of the present invention to provide a method capable of appropriately preventing generation and poor adhesion of an insulating film and stably producing a high silicon steel sheet having excellent surface properties.

[0011]

The present invention for achieving the above object is based on the idea of reducing the dew point and the oxygen concentration in the furnace atmosphere to predetermined levels as disclosed in Japanese Patent Application Laid-Open No. 6-212397. Changing the idea, the carbon contained in the steel sheet and the furnace atmosphere were assumed to be inevitably present in the furnace atmosphere of the The reaction between the oxygen content in the atmosphere and the SiCl ₄ is suppressed by reacting with the oxygen content (including oxygen in the water) (decarburization reaction), thereby preventing the formation of silica. The configuration is as follows.

(1) A steel sheet containing less than 4 wt% of Si is subjected to a siliconizing treatment at a treatment temperature of 1023 to 1200 ° C. in a non-oxidizing gas atmosphere containing SiCl ₄ in a siliconized zone,
Next, in a non-oxidizing gas atmosphere containing no SiCl ₄ ,
By performing a diffusion heat treatment for diffusing i into the steel sheet,
In a method of continuously producing high silicon steel sheets, a steel sheet containing an amount of carbon satisfying the following equation according to the atmosphere in the furnace of the siliconized zone is used as a base steel sheet to be subjected to siliconizing treatment. A method for producing a high-silicon steel sheet having excellent surface properties. 0.2 [O] -27 ≦ [C] ≦ 0.3 [O] +116 where [O]: oxygen equivalent in the furnace (ppm) [C]: carbon content of the base steel sheet (ppm)

(2) A steel sheet containing less than 4 wt% of Si is subjected to a siliconizing treatment at a treatment temperature of 1023 to 1200 ° C. in a non-oxidizing gas atmosphere containing SiCl ₄ in a siliconized zone,
Next, in a non-oxidizing gas atmosphere containing no SiCl ₄ ,
By performing a diffusion heat treatment for diffusing i into the steel sheet,
In a method of continuously producing high silicon steel sheets, a steel sheet containing an amount of carbon satisfying the following equation according to the atmosphere in the furnace of the siliconized zone is used as a base steel sheet to be subjected to siliconizing treatment. A method for producing a high-silicon steel sheet having excellent surface properties. 0.2 [O] -27≤ [C] ≤0.3 [O] +66 ... [O]: Oxygen equivalent in the furnace (ppm) [C]: Carbon content of the base steel sheet (ppm)

(3) A steel sheet containing less than 4% by weight of Si is subjected to a siliconizing treatment at a processing temperature of 1023 to 1200 ° C. in a non-oxidizing gas atmosphere containing SiCl ₄ in a siliconized zone,
Next, in a non-oxidizing gas atmosphere containing no SiCl ₄ ,
By performing a diffusion heat treatment for diffusing i into the steel sheet,
In a method of continuously producing high silicon steel sheets, a steel sheet containing an amount of carbon satisfying the following equation according to the atmosphere in the furnace of the siliconized zone is used as a base steel sheet to be subjected to siliconizing treatment. A method for producing a high-silicon steel sheet having excellent surface properties. 0.2 [O] + 5 ≦ [C] ≦ 0.3 [O] +66 ... [O]: Oxygen equivalent in the furnace (ppm) [C]: Carbon content of the base steel sheet (ppm)

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, when moisture or oxygen is present in the atmosphere of a siliconized zone, SiCl ₄ is oxidized to silica (SiO ₂ ). In particular, 1023-120
At a siliconizing temperature of 0 ° C., SiCl ₄ is easily oxidized on the steel sheet surface, and the generated silica adheres to the steel sheet surface. Oxygen equivalent [O] ([O] = [H ₂ O] +2) in atmosphere of siliconized zone
[O ₂ ], where [H ₂ O]: concentration of water vapor in the atmosphere (pp
m), [O ₂ ]: When the oxygen concentration (ppm) in the atmosphere is relatively high, the silica adhering to the steel sheet surface becomes powdery, which is transferred and accumulated on the hearth roll in the furnace, and causes a pressing flaw on the steel sheet surface. wear. When the oxygen equivalent in the atmosphere is relatively low, an adhesive silica film is formed on the surface of the steel sheet, which is also transferred to a hearth roll and causes a pressing flaw.

However, when a sufficient amount of carbon is introduced into an atmosphere containing SiCl ₄ + H ₂ O (O ₂ ), the carbon exhibits an extremely high reducing ability, and all H ₂ O (O ₂ ) reacts with carbon. Therefore, generation of silica can be suppressed. on the other hand,
When the dew point and oxygen concentration of the atmosphere in the furnace are relatively high, carbon in the steel sheet reacts with water or oxygen and escapes as CO gas when annealed at a high temperature (decarburization reaction). Therefore, in the present invention, utilizing such a decarburizing effect, a steel sheet containing a certain amount of carbon in advance is used as a base steel sheet before the siliconizing treatment, and the carbon in the steel sheet and the atmospheric By reacting with water and oxygen (decarburization reaction), oxidation of SiCl _{4 on} the steel sheet surface during siliconizing is suppressed, thereby suppressing generation of silica. Since the generation of silica is caused by the oxidation of SiCl _{4 on} the surface of the steel sheet, lowering the oxygen concentration especially near the surface of the steel sheet suppresses the generation of silica, that is, reduces the pickup. In this regard, in the method of the present invention, the reaction of carbon in the steel sheet and the oxygen content in the atmosphere reduces the oxygen concentration in the vicinity of the steel sheet surface, so that the generation of silica can be effectively suppressed.

FIG. 1 shows that the carbon content was 24 pp each.
1 shows an appearance photograph of the surface of a sample obtained by subjecting a base steel sheet having a m of 112 ppm to a siliconizing treatment in an atmosphere having a dew point of -28 ° C. and an oxygen concentration of 20 ppm and performing a diffusion treatment. According to this,
While the silica film adheres to the surface of the sample having a base material steel plate having a carbon content of 24 ppm, no silica is observed to be adhered to the surface of the sample having a base material steel plate having a carbon content of 112 ppm. As described above, it has been found that by containing an appropriate amount of carbon in the base steel sheet, it is possible to suppress the formation of a silica film on the steel sheet surface even when the oxygen content in the atmosphere is relatively large. Then, the carbon content of the steel sheet after the above-mentioned siliconizing treatment was reduced to 10 ppm and 25 ppm, respectively, and it became clear that the decarburizing reaction was proceeding simultaneously with the siliconizing reaction. That is, as a chemical reaction, the following formula (1) proceeds more preferentially than formula (2), which means that the production of silica (SiO ₂ ) is suppressed. C + H ₂ O → CO + H ₂ (1) SiCl ₄ + 2H ₂ O → SiO ₂ + 4HCl (2)

[0018] Thus, although in order to suppress the formation of silica it was revealed that it is extremely effective to use a decarburization of carbon contained in the steel sheet, SiCl ₄
The carbon content in the base steel sheet required to suppress the reaction between H ₂ O and O ₂
And the amount of H ₂ O (dew point). Therefore, the amounts of O ₂ and H ₂ O in the atmosphere of the siliconized zone were variously changed, and the base steel sheets having different carbon contents were subjected to the siliconizing treatment, and the formation state of the silica film on the surface thereof was observed. The result is shown in FIG. According to this, it has been found that, in order to suppress the generation of silica, it is necessary to increase the carbon content of the base steel sheet as the O ₂ amount and the H ₂ O amount in the siliconized zone atmosphere increase.

Specifically, in order to suppress the formation of thin film-like silica on the surface of the steel sheet, the water vapor concentration [H ₂ O] (ppm) and the oxygen concentration [O ₂ ] (ppm) in the atmosphere of the silicidized zone are controlled. [O] (ppm) ([O] = [H]
₂ O] +2 [O ₂ ]) and the carbon content [C] of the base steel sheet were found to require the following relationship. 0.2 [O] -27 ≦ [C] (3) Further, it was found that the following conditions had to be satisfied in order to suppress the adhesion of the powdery silica to the steel sheet. 0.2 [O] + 5 ≦ [C] (4) Therefore, in the present invention, the above formula (3), more preferably the above (4)
The lower limit value of the carbon content [C] of the base steel sheet was calculated using the equation.

As described above, in the present invention, a predetermined amount or more of carbon is previously contained in the base steel sheet in accordance with the oxygen equivalent [O] in the atmosphere of the silicified zone, and the decarburization reaction of this carbon is utilized to obtain silica. On the other hand, it is not desirable from the viewpoint of magnetic properties that excessive carbon remains in the final product from the viewpoint of magnetic properties.Therefore, the upper limit of the carbon content of the base steel sheet deteriorates the magnetic properties after decarburization. It is necessary to specify from the viewpoint of leaving an amount of carbon that is not allowed to remain. The effect of the carbon content on the magnetic properties of the high silicon steel sheet manufactured by the siliconizing treatment method was investigated.
pm or less, there is substantially no adverse effect on magnetic properties, and the carbon content is more than 50 ppm to 100 pp.
It was found that even with m, the magnetic properties could be ensured for practical use although the magnetic properties were slightly inferior.

The relationship between the oxygen equivalent [O] in the atmosphere of the silicide zone and the decarburization amount was investigated under the above premise, and it was determined that the carbon content of the steel sheet after the siliconizing treatment was 100 ppm or less. It was clarified that the following equation (5) had to be satisfied, and the following equation (6) had to be satisfied in order to reduce the carbon content of the steel sheet after the siliconizing treatment to 50 ppm or less. [C] ≦ 0.3 [O] +116 (5) [C] ≦ 0.3 [O] +66 (6) Therefore, in the present invention, the above formula (5), more preferably the above formula (5)
The upper limit of the carbon content [C] of the base steel sheet was determined by the equation (6).

From the above results, in order to produce a high silicon steel sheet having excellent magnetic properties while suppressing the formation of silica, the amount of carbon contained in the base steel sheet before the siliconizing treatment satisfies the following equation. There is a need. 0.2 [O] -27≤ [C] ≤0.3 [O] +116 ... [O]: Oxygen equivalent (ppm) in the atmosphere of the siliconized zone [C]: Carbon content of the base steel sheet (ppm) In order to further suppress the generation of powdery silica, it is necessary to satisfy the following expression, and to ensure better magnetic properties, it is necessary to satisfy the following expression. 0.2 [O] -27≤ [C] ≤0.3 [O] +66 ... 0.2 [O] + 5≤ [C] ≤0.3 [O] +66 ...

However, as described above, it is actually very difficult to control and control the dew point and oxygen concentration of the atmosphere in the siliconized zone to low levels, and this is a boundary of the control and management of the atmosphere. Dew point and oxygen concentration level are as follows:
28 ° C., oxygen concentration: approximately 50 ppm, which corresponds to approximately 560 ppm in terms of oxygen equivalent [O] in the furnace atmosphere.
In other words, if the atmosphere of the siliconized zone is maintained and controlled at a dew point of about -28 ° C. or more and an oxygen concentration of about 50 ppm or more, the control is not so difficult. Therefore, when the present invention is carried out under operating conditions in which the atmosphere of the siliconized zone has a dew point of about -28 ° C. or more and an oxygen concentration of about 50 ppm or more (corresponding to about 560 ppm or more in terms of oxygen equivalent [O]), It can be said that the invention has the highest practical utility. Assuming that the furnace atmosphere is easy to control and manage as described above, the carbon content of the base steel sheet used in the production method of the present invention is 85 to 85 according to the above equation.
284 ppm, 85 to 234 ppm according to the above formula,
Further, according to the above formula, it is 117 to 234 ppm, and in any case, a base material steel sheet having a carbon content of more than 50 ppm is used.

It is generally considered that the upper limit of the carbon content of a high silicon steel sheet should be 100 ppm or less, substantially about 50 ppm, in order to avoid deterioration of magnetic properties. In this regard, a steel sheet having a carbon content of 50 ppm or less has been used as a base material steel sheet subjected to a siliconizing treatment. Therefore, it can be said that performing a siliconizing treatment using a steel sheet having a high carbon content as a base material steel sheet as described above is a method beyond conventional common sense. In the production of a high silicon steel sheet by the continuous siliconizing treatment method which is a target of the present invention, a processing gas having a SiCl ₄ concentration of about 5 to 35 mol% is usually supplied to the siliconized zone,
The siliconizing treatment is performed at a treatment temperature of 1023 to 1200 ° C. Further, the silicon content of the manufactured high silicon steel sheet is arbitrary, but generally, a high silicon steel sheet having Si: 5 to 10 wt% is manufactured.

Hereinafter, specific embodiments of the present invention will be described. Example 1 In a continuous siliconizing line as shown in FIG. 3, a base steel sheet (sheet thickness: 0.1 mm) having various carbon contents of Si: 3.0 wt% was dew point: -28 ° C. ([ H ₂
O] = 460 ppm), a silicon carbide treatment in an atmosphere (oxygen equivalent [O]: 560 ppm) with an oxygen concentration of 50 ppm to produce a high silicon steel sheet with 6.5 wt% Si, and the steel sheet at that time. The silica generation state on the surface, the amount of pick-up (the amount of plate flaws), the amount of residual carbon, and the magnetic properties were examined. Table 1 shows the results. According to this, when the oxygen equivalent [O] of the silicon-silicon atmosphere is 560 ppm, the use of a base steel sheet having a carbon content of 85 ppm or more suppresses the formation of a silica film and reduces the amount of pickup generated. ing. Further, by using a base steel sheet having a carbon content of 117 ppm or more, the generation of powdery silica is also suppressed, and the generation amount of the pickup is zero.

Further, from the viewpoint of magnetic properties, when a base steel sheet having a carbon content exceeding 284 ppm is used, the carbon content exceeds 100 ppm even after siliconizing,
For this reason, iron loss is extremely high. On the other hand, when a base steel sheet having a carbon content of 284 ppm or less is used, the carbon content after the siliconizing treatment is 100 ppm or less,
Almost good iron loss is obtained. In addition, the carbon content is 2
When a base steel sheet of 34 ppm or less is used, the carbon content after the siliconizing treatment is 50 ppm or less, and better magnetic properties are obtained.

[0027]

[Table 1]

Example 2 In a continuous siliconizing line as shown in FIG. 3, Si having various carbon contents:
Dew point: -3 for 0 wt% base steel sheet (sheet thickness: 0.3 mm)
5 ° C. ([H ₂ O] = 250 ppm), oxygen concentration: 25 p
A high silicon steel sheet having a Si content of 6.3 wt% was produced by performing a siliconizing treatment in a siliconizing zone having an atmosphere of pm (oxygen equivalent [O]: 300 ppm). (Sheet flaw generation amount), residual carbon amount and magnetic properties were examined. Table 2 shows the results. According to this, when the oxygen equivalent [O] of the silicon-silicon atmosphere is 300 ppm, the use of a base steel sheet having a carbon content of 33 ppm or more suppresses the formation of a silica film and reduces the amount of pickup generated. ing. In addition, by using a base steel sheet having a carbon content of 65 ppm or more, generation of powdery silica is suppressed,
The amount of pickup generated is zero.

From the viewpoint of magnetic properties, when a base steel sheet having a carbon content exceeding 206 ppm is used, the carbon content exceeds 100 ppm even after siliconizing,
For this reason, iron loss is extremely high. In contrast, when a base material steel sheet having a carbon content of 206 ppm or less is used, the carbon content after the siliconizing treatment becomes 100 ppm or less,
Almost good iron loss is obtained. In addition, the carbon content is 1
When a base steel sheet of 56 ppm or less is used, the carbon content after the siliconizing treatment is 50 ppm or less, and better magnetic properties are obtained.

[0030]

[Table 2]

[0031]

According to the first aspect of the present invention described above, even when the dew point and the oxygen concentration of the atmosphere of the siliconized zone are relatively high, the formation of the silica film on the surface of the steel sheet in the siliconized zone is prevented. Properly prevents high silicon steel sheet with excellent surface properties, no pick-up due to the formation of silica film, good adhesion of insulating film, and good magnetic properties. Can be manufactured.

Further, according to the invention of claim 2 of the present application, it is possible to stably produce a high-silicon steel sheet having the same excellent surface properties as the invention of claim 1 and having even better magnetic properties. Can be. Further, according to the invention of claim 3 of the present application, it is possible to appropriately prevent not only the formation of the silica film on the surface of the steel sheet but also the generation of the silica powder, and thus the occurrence of the pickup caused by the generation of the silica is prevented. It is possible to stably produce a high-silicon steel sheet having excellent surface properties with little or no adhesion and good adhesion of the insulating film, and further having better magnetic properties as compared with the first aspect of the present invention.

[Brief description of the drawings]

FIG. 1 is a photograph showing the appearance of the surface of a sample obtained by subjecting a base steel sheet having a carbon content of 24 ppm and 112 ppm to a siliconizing treatment.

FIG. 2 is a graph showing the state of silica generation on the surface of a steel sheet when siliconizing treatment is performed in atmospheres of various oxygen equivalents [O].

FIG. 3 is an explanatory view showing a continuous siliconizing line.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhisa Okada, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Hironori Ninomiya 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (58) Investigated field (Int. Cl. ⁷ , DB name) C23C 10/08 C21D 1/76

Claims (3)

(57) [Claims] 1. A steel sheet containing less than 4 wt% of Si:
Diffusion heat treatment of the immersion珪帯and siliconizing treatment at a treatment temperature of 1,023 to 1,200 ° C. in a non-oxidizing gas atmosphere containing SiCl _4, then to diffuse Si in the steel sheet inside in a non-oxidizing gas atmosphere containing no SiCl ₄ In the method of continuously producing high silicon steel sheets, a steel sheet containing an amount of carbon that satisfies the following equation according to the atmosphere in the furnace of the siliconized zone as a base metal steel sheet to be subjected to siliconizing treatment. A method for producing a high silicon steel sheet having excellent surface properties, comprising using 0.2 [O] -27≤ [C] ≤0.3 [O] +116 ... [O]: Oxygen equivalent in furnace atmosphere (ppm) [C]: Carbon content of base steel sheet (ppm) 2. A steel sheet containing less than 4 wt% of Si:
Diffusion heat treatment of the immersion珪帯and siliconizing treatment at a treatment temperature of 1,023 to 1,200 ° C. in a non-oxidizing gas atmosphere containing SiCl _4, then to diffuse Si in the steel sheet inside in a non-oxidizing gas atmosphere containing no SiCl ₄ In the method of continuously producing high silicon steel sheets, a steel sheet containing an amount of carbon that satisfies the following equation according to the atmosphere in the furnace of the siliconized zone as a base metal steel sheet to be subjected to siliconizing treatment. A method for producing a high silicon steel sheet having excellent surface properties, comprising using 0.2 [O] -27≤ [C] ≤0.3 [O] +66 ... [O]: Oxygen equivalent in furnace atmosphere (ppm) [C]: Carbon content of base steel sheet (ppm) 3. A steel sheet containing less than 4 wt% of Si:
Diffusion heat treatment of the immersion珪帯and siliconizing treatment at a treatment temperature of 1,023 to 1,200 ° C. in a non-oxidizing gas atmosphere containing SiCl _4, then to diffuse Si in the steel sheet inside in a non-oxidizing gas atmosphere containing no SiCl ₄ In the method of continuously producing high silicon steel sheets, a steel sheet containing an amount of carbon that satisfies the following equation according to the atmosphere in the furnace of the siliconized zone as a base metal steel sheet to be subjected to siliconizing treatment. A method for producing a high silicon steel sheet having excellent surface properties, comprising using 0.2 [O] + 5 ≦ [C] ≦ 0.3 [O] +66 where [O]: Oxygen equivalent in furnace atmosphere (ppm) [C]: Carbon content of base steel sheet (ppm)