JPH08209325A - Production of high silicon steel sheet excellent in surface characteristic - Google Patents

Abstract

PURPOSE: To produce a high silicon steel sheet excellent in surface characteristic by specifying carbon content in a steel sheet as a base material to be siliconized, at the time of producing a high silicon steel sheet by siliconizing a steel sheet containing Si by a specific amount or less. CONSTITUTION: A steel sheet containing <4wt.% Si is siliconized in a siliconizing zone in an SiCl4 -containing nonoxidizing gas atmosphere and then subjected to diffusion heat treatment for diffusing Si into the inner part of the steel sheet in an SiCl4 -free nonoxidizing gas atmosphere, by which the high silicon steel sheet is continuously produced. At this time, as the steel sheet as a base material to be siliconized, a steel sheet containing carbon by the amount satisfying inequality is used, according to the atmosphere in the furnace in the siliconizing zone. In the inequality, (O) is oxygen equivalent (ppm) in the atmosphere in the furnace and (C) is carbon content (ppm) in the steel sheet as base material. By this method, carbon in the steel sheet is allowed to react with oxygen in the atmosphere and the reaction between the oxygen in the atmosphere and SiCl4 is inhibited and the formation of silica can be inhibited, and as a result, the occurrence of picking-up and inferior adhesiveness of insulating film can be prevented.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As a method for industrially producing a high silicon steel sheet having a Si content of 4 wt% or more, JP-A-62-1270.
A siliconizing method shown in Japanese Patent No. 78 is known. In this manufacturing method, a thin steel sheet containing Si: less than 4 wt% is SiCl
₄ is a method of infiltrating Si by reacting with ₄ at a high temperature and diffusing the infiltrated Si in the plate thickness direction to obtain a high silicon steel sheet, for example, JP-A-62-227078.
In Japanese Patent Laid-Open No. 62-26324 and Japanese Patent Laid-Open No. 62-26324, a steel sheet is subjected to a continuous siliconizing treatment 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. We have obtained high silicon steel sheet.

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

In order to continuously perform the siliconizing treatment on the steel sheet by such a process, a continuous siliconizing treatment line as shown in FIG. 3 is used. This continuous siliconizing treatment line is equipped with a heating zone, a siliconizing zone, a diffusion soaking zone and a cooling zone from the inlet side, and the steel sheet is continuously heated in the heating zone up to the treatment temperature and then reacted with SiCl _{4 in the} siliconizing zone. By Si
And then continuously undergoing a heat treatment for diffusing Si in the plate thickness direction in the diffusion soaking zone, and then cooling in a cooling zone to produce a coiled high silicon steel plate.

[0005]

By the way, when a high silicon steel sheet is produced by the above continuous siliconizing line, there is a problem that the steel sheet being produced is flawed and the quality of the product steel sheet is deteriorated. . The present inventors have repeatedly studied the cause of such a problem, and as a result, silica produced by the reaction of SiCl ₄ with a trace amount of oxygen and moisture in the atmosphere in the siliconized zone causes a flaw in the steel sheet. I found out that it was the main cause. It was also found that the silica adheres to the steel sheet in a powder form or a thin film form, thereby deteriorating the adhesion of the insulating film.

That is, a large amount of reaction gas SiCl ₄ is supplied to the siliconized zone for infiltrating Si, but since this SiCl ₄ is a very active gas, it reacts directly with the steel sheet. First, silica (SiO ₂ ) is produced by reacting with a slight amount of oxygen and water in the atmosphere in the furnace as shown in the following formula. SiCl ₄ + O ₂ → SiO ₂ + 2Cl ₂ SiCl ₄ + 2H ₂ O → SiO ₂ + 4HCl

This silica is produced in the gas phase or on the surface of the steel sheet by the above reaction and adheres to the steel sheet in the form of powder or thin film. The silica powder attached to the lower surface of the steel sheet is used for conveying the steel sheet provided in the furnace. Adheres to the surface of the hearth roll. And
It was found that the adhesion of the silica powder causes unevenness on the hearth roll surface, and the unevenness causes a flaw on the steel sheet heated to a high temperature (this phenomenon is called a pickup). In addition, silica powder generated in the gas phase adheres to and accumulates on the refractory surface in the furnace and contaminates the inside of the furnace.
The silica powder adhering to the surface of the refractory material falls on the steel plate or hearth roll and may scratch the steel plate.Furthermore, the powdery or thin film silica adhering to the steel plate surface deteriorates the adhesion of the insulating film. I also understood that. Therefore,
As a measure for suppressing the formation of such silica, it is considered that the atmosphere is controlled so as to reduce the oxygen concentration and the dew point in the atmosphere in the siliconized zone as much as possible.

In a general continuous annealing line, in order to suppress the oxidation of the steel sheet surface, the oxygen concentration and the dew point (steam concentration) in the furnace are maintained below a certain level, but the operation is carried out.
Regarding the atmosphere in the furnace of the continuous siliconizing treatment line, for example,
In JP-A-6-212397, when the 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 the grain boundaries are oxidized, and the bending workability of the product deteriorates. It is pointed out that, in the publication, therefore, the oxygen concentration in the atmosphere in the furnace is 45 p as a condition for preventing the oxidation of the steel sheet surface and the crystal grain boundaries and producing a product having good workability.
pm or less, dew point -30 ° C or less, and oxygen concentration [O ₂ ]
It has been proposed to control the atmosphere in the furnace such that (ppm) and water vapor concentration [H ₂ O] (ppm) satisfy the conditions of the following equation.

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

Particularly in recent years, the use ratio of fiber-based refractory materials having excellent heat insulating properties as the refractory material in the furnace has been increasing, and since the fiber-based refractory material has a high porosity, H ₂ O is used.
Is easily absorbed, and when the furnace is opened to the atmosphere immediately after the construction of the furnace or at the time of repairing or inspecting the furnace, a large amount of air or moisture is absorbed therein. Therefore, the moisture and air absorbed in the refractory material gradually leach into the atmosphere in the furnace during the operation, and it is extremely difficult to control the atmosphere in the siliconized zone. Therefore, it is actually not easy to control the atmosphere in the furnace as in JP-A-6-212397.
Even if such a low dew point and a low oxygen concentration could be achieved at the beginning of the furnace operation, the dew point and the oxygen concentration would increase and the pickup would occur if the operation was continued for a certain period of time.

Therefore, the object of the present invention is to suppress the formation of silica in the siliconized zone even when the dew point or oxygen concentration of the furnace atmosphere of the siliconized zone is relatively high, and to pick up due to the formation of silica. An object of the present invention is to provide a method capable of appropriately preventing the occurrence and poor adhesion of an insulating film and stably manufacturing a high silicon steel sheet having excellent surface properties.

[0011]

SUMMARY OF THE INVENTION The present invention for achieving the above object is based on the idea of reducing the dew point and oxygen concentration of a furnace atmosphere to predetermined levels as disclosed in Japanese Patent Laid-Open No. 6-212397. Changing the idea, and assuming that it is inevitable that a certain amount of moisture and oxygen are present in the furnace atmosphere of the siliconized zone, the carbon contained in the steel sheet and the furnace atmosphere By reacting (decarburizing reaction) with the oxygen content (including oxygen in water) of the above, the reaction between the oxygen content in the atmosphere and SiCl ₄ is suppressed, thereby preventing the formation of silica. , Its configuration is as follows.

(1) Si: A steel sheet containing less than 4 wt% is subjected to a siliconizing treatment in an atmosphere of non-oxidizing gas containing SiCl ₄ in a siliconizing zone, and then in an atmosphere of non-oxidizing gas containing no SiCl _4. In the method of continuously producing a high-silicon steel sheet by performing a diffusion heat treatment for diffusing Si into the steel sheet, the following formula is used as a base material steel sheet to be subjected to the siliconizing treatment according to the atmosphere in the siliconizing zone. A method for producing a high silicon steel sheet having excellent surface properties, which comprises using a steel sheet containing a satisfactory amount of carbon. 0.2 [O] −27 ≦ [C] ≦ 0.3 [O] +116, where [O]: oxygen equivalent in the furnace (ppm) [C]: carbon content of base material steel plate (ppm)

(2) Si: A steel sheet containing less than 4 wt% is subjected to a siliconizing treatment in a siliconizing zone in a non-oxidizing gas atmosphere containing SiCl _4, and then in a non-oxidizing gas atmosphere containing no SiCl _4. In the method of continuously producing a high-silicon steel sheet by performing a diffusion heat treatment for diffusing Si into the steel sheet, the following formula is used as a base material steel sheet to be subjected to the siliconizing treatment according to the atmosphere in the siliconizing zone. A method for producing a high silicon steel sheet having excellent surface properties, which comprises using a steel sheet containing a satisfactory amount of carbon. 0.2 [O] −27 ≦ [C] ≦ 0.3 [O] +66, where [O]: oxygen equivalent in the furnace (ppm) [C]: carbon content of base material steel plate (ppm)

(3) Si: A steel sheet containing less than 4 wt% is subjected to a siliconizing treatment in an atmosphere of non-oxidizing gas containing SiCl ₄ in a siliconizing zone, and then in an atmosphere of non-oxidizing gas containing no SiCl _4. In the method of continuously producing a high-silicon steel sheet by performing a diffusion heat treatment for diffusing Si into the steel sheet, the following formula is used as a base material steel sheet to be subjected to the siliconizing treatment according to the atmosphere in the siliconizing zone. A method for producing a high silicon steel sheet having excellent surface properties, which comprises using a steel sheet containing a satisfactory amount of carbon. 0.2 [O] + 5 ≦ [C] ≦ 0.3 [O] +66, where [O]: oxygen equivalent (ppm) in the furnace [C]: carbon content (ppm) of the base steel sheet

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, when water or oxygen is present in the atmosphere of the siliconized zone, SiCl ₄ is oxidized into silica (SiO ₂ ). Especially 1023-120
At a siliconizing temperature of 0 ° C., SiCl ₄ is easily oxidized on the surface of the steel sheet, and the produced silica adheres to the surface of the steel sheet. Oxygen equivalent [O] ([O] = [H ₂ O] +2
[O ₂ ] where [H ₂ O]: water vapor concentration in the atmosphere (pp
m), [O ₂ ]: When the oxygen concentration (ppm) in the atmosphere is relatively high, the silica adhering to the steel plate surface becomes powdery, which is transferred / accumulated on the hearth roll in the furnace and scratches the steel plate surface. wear. Further, when the oxygen equivalent [O] in the atmosphere is relatively low, an adherent silica film is formed on the surface of the steel sheet, but this is also transferred to the hearth roll and causes scratches.

However, when a sufficient amount of carbon is put 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, the carbon in the steel sheet reacts with water or oxygen to escape as CO gas when annealed at high temperature (decarburization reaction). Therefore, in the present invention, by utilizing such a decarburizing action, 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 atmosphere By reacting with water and oxygen (decarburization reaction), the oxidation of SiCl _{4 on} the surface of the steel sheet during siliconizing is suppressed, and thereby the formation of silica is suppressed. Since the generation of silica is caused by the oxidation of SiCl _{4 on} the surface of the steel sheet, particularly lowering the oxygen concentration near the surface of the steel sheet suppresses the generation of silica, that is, the number of pickups. In this respect, in the method of the present invention, the oxygen concentration in the vicinity of the surface of the steel sheet is lowered by the reaction of carbon in the steel sheet and the oxygen content in the atmosphere, so that the generation of silica can be effectively suppressed.

In FIG. 1, the carbon content is 24 pp each.
The external appearance photograph of the surface of the sample obtained by carrying out the siliconizing treatment and the diffusion treatment of the base material steel sheet of m, 112 ppm in a dew point: -28 degreeC, oxygen concentration: 20 ppm is shown. According to this,
While the silica film adheres to the surface of the sample having a carbon content of 24 ppm of the base material steel sheet, the adhesion of silica is not recognized to the surface of the sample having a carbon content of 112 ppm of the base material steel sheet. As described above, it has been found that, by containing an appropriate amount of carbon in the base steel sheet, the formation of a silica film on the surface of the steel sheet can be suppressed even if the oxygen content in the atmosphere is relatively large. Then, the carbon contents of the steel sheet after the above-mentioned siliconizing treatment were reduced to 10 ppm and 25 ppm, respectively, and it became clear that the decarburizing reaction was proceeding at the same time as the siliconizing reaction. That is, as the chemical reaction, the following formula (1) proceeds preferentially over the formula ( ₂ ), and thus 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)

As described above, it has been revealed that it is extremely effective to utilize the decarburization reaction of carbon contained in the steel sheet in order to suppress the formation of silica, but SiCl ₄
And H the carbon content of the base steel sheet required to suppress the reaction between the ₂ O is of course immersed O ₂ in珪帯atmosphere
Amount and H ₂ O amount (dew point). For this reason, the amounts of O ₂ and H ₂ O in the atmosphere of the siliconizing zone were variously changed, the base material steel sheets having different carbon contents were siliconized, and the state of formation of the silica film on the surface was observed. The result is shown in FIG. According to this, in order to suppress the formation of silica, it has been found that it is necessary to increase the carbon content of the base steel sheet as the O ₂ content and the H ₂ O content in the atmosphere of the siliconizing zone increase.

Specifically, in order to suppress the formation of thin film 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 siliconizing zone are set. Oxygen equivalent [O] (ppm) ([O] = [H
It has been found that the following relationship is required between ( ₂ O] +2 [O ₂ ]) and the carbon content [C] of the base steel sheet. 0.2 [O] −27 ≦ [C] (3) Further, it was found that the following conditions must be satisfied in order to suppress the adhesion of powdery silica to the steel plate. 0.2 [O] + 5 ≦ [C] (4) Therefore, in the present invention, the above formula (3) is more preferable, and the above (4) is more preferable.
The formula was used as the lower limit of the carbon content [C] of the base steel sheet.

As described above, according to the present invention, the base steel sheet is preliminarily made to contain a certain amount or more of carbon in accordance with the oxygen equivalent [O] in the atmosphere of the silica zone, and the decarburization reaction of this carbon is utilized to form silica. Although it suppresses the generation, on the other hand, excessive carbon residue in the final product is not preferable from the viewpoint of magnetic properties, and therefore the upper limit of the carbon content of the base steel sheet deteriorates the magnetic properties after decarburization. It is necessary to specify it from the viewpoint of leaving an amount of carbon that does not allow it to remain. When the effect of carbon content on the magnetic properties of the high silicon steel sheet produced by the siliconizing method was investigated, it was found that the carbon content was 50p.
If it is pm or less, it does not substantially affect the magnetic properties, and the carbon content exceeds 50 ppm to 100 pp.
It has been found that even if m, the magnetic characteristics are slightly inferior, but the practical magnetic characteristics can be secured.

Under such a premise, the relationship between the oxygen equivalent [O] and the decarburization amount in the atmosphere of the siliconizing zone was investigated, and it was found that the carbon content of the steel sheet after the siliconizing treatment was 100 ppm or less. It has become clear that it is necessary to satisfy the following formula (5) and the following formula (6) 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) is more preferable, and the above formula (5) is more preferable.
The upper limit of the carbon content [C] of the base steel sheet was defined 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 carbon content in the base steel sheet before the siliconizing treatment satisfies the following formula. There is a need. 0.2 [O] -27 ≤ [C] ≤ 0.3 [O] +116, where [O]: oxygen equivalent (ppm) in the atmosphere of siliconizing zone [C]: carbon content of base material steel plate (ppm) Further, it is necessary to satisfy the following formula in order to suppress the generation of powdery silica, and it is necessary to satisfy the following formula in order to secure better magnetic properties. 0.2 [O] −27 ≦ [C] ≦ 0.3 [O] +66 ... 0.2 [O] + 5 ≦ [C] ≦ 0.3 [O] +66 ...

By the way, as described above, it is actually very difficult to control and manage the dew point and oxygen concentration of the atmosphere in the siliconized zone to a low level, which is the boundary of the atmosphere control and management. Dew point and oxygen concentration level are:
28 ° C., oxygen concentration: about 50 ppm, which corresponds to about 560 ppm in oxygen equivalent [O] in the atmosphere in the furnace.
That is, if the atmosphere of the siliconized zone is maintained and maintained at a dew point of about −28 ° C. or higher and an oxygen concentration of about 50 ppm or higher, its control is not so difficult. Therefore, when the present invention is carried out under the operating conditions in which the atmosphere of the siliconized zone is set to have 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 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 manufacturing method of the present invention is 85 to 85 according to the above formula.
284 ppm, 85-234 ppm according to the above formula,
Further, according to the above formula, it becomes 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 carbon content of the high silicon steel sheet should be 100 ppm or less, and substantially 50 ppm or so, in order to avoid deterioration of magnetic properties, and therefore, the conventional siliconizing treatment is required. Then, a steel sheet having a carbon content of 50 ppm or less has been used as a base material steel sheet subjected to the siliconizing treatment. Therefore, it can be said that performing the siliconizing treatment using a steel plate having a high carbon content as the base steel plate as described above is a method beyond the conventional wisdom. In the production of a high silicon steel sheet by the continuous siliconizing treatment method targeted by the present invention, a processing gas having a SiCl ₄ concentration of about 5 to 35 mol% is usually supplied to the siliconized zone, and the steel sheet has a temperature of 1023 to 1200 ° C. Silicid treatment is performed at a treatment temperature. The silicon content of the manufactured high-silicon steel plate is arbitrary, but a high-silicon steel plate of Si: 5 to 10 wt% is generally manufactured.

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

Further, from the viewpoint of magnetic properties, when a base material steel sheet having a carbon content of more than 284 ppm is used, the carbon content exceeds 100 ppm even after the siliconizing,
Therefore, iron loss is extremely high. On the other hand, when a base material 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. Furthermore, the carbon content is 2
When a base material 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]

[Embodiment 2] In a continuous siliconizing treatment line as shown in FIG. 3, Si: 3.
0 wt% base material steel plate (plate thickness: 0.3 mm) dew point: -3
5 ° C ([H ₂ O] = 250ppm), oxygen concentration: 25p
A silicon-impregnated zone in a pm atmosphere (oxygen equivalent [O]: 300 ppm) is subjected to a silicidation treatment to produce a Si: 6.3 wt% high-silicon steel sheet. (Amount of board defects), residual carbon amount and magnetic properties were examined. The results are shown in Table 2. According to this, when the oxygen equivalent [O] of the atmosphere in the siliconized zone is 300 ppm, by using the base material steel sheet having the carbon content of 33 ppm or more, the production of the silica film is suppressed and the pickup generation amount is reduced. ing. In addition, generation of powdery silica is suppressed by using a base material steel sheet having a carbon content of 65 ppm or more,
The amount of pickup generated is zero.

Further, from the viewpoint of magnetic properties, when a base steel sheet having a carbon content of more than 206 ppm is used, the carbon content exceeds 100 ppm even after the siliconizing,
Therefore, iron loss is extremely high. On the other hand, when a base material steel sheet having a carbon content of 206 ppm or less is used, the carbon content after the siliconizing treatment is 100 ppm or less,
Almost good iron loss is obtained. Furthermore, the carbon content is 1
When a base steel sheet of 56 ppm or less was used, the carbon content after the siliconizing treatment was 50 ppm or less, and better magnetic characteristics were obtained.

[0030]

[Table 2]

[0031]

According to the invention of claim 1 of the present application described above, even if the dew point and oxygen concentration of the atmosphere in the siliconizing zone are relatively high, a silica film is formed on the surface of the steel sheet in the siliconizing zone. Stable high silicon steel sheet that has an excellent surface property that can be appropriately prevented, and therefore does not generate pickup due to the formation of a silica film and has good adhesion of the insulating film. Can be manufactured.

Further, according to the invention of claim 2 of the present application, it is possible to stably manufacture a high silicon steel sheet having the same excellent surface texture as that of the invention of claim 1 and more excellent magnetic characteristics. You can Further, according to the invention of claim 3 of the present application, not only the production of the silica film on the surface of the steel sheet but also the production of the silica powder can be appropriately prevented, so that the occurrence of the pickup due to the production of silica occurs. It is possible to stably manufacture a high silicon steel sheet which has almost no surface and excellent adhesiveness of the insulating film and has excellent magnetic properties as compared with the invention of claim 1.

[Brief description of drawings]

FIG. 1 is a photograph showing the appearance of the surface of a sample obtained by subjecting a base steel sheet having carbon contents 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 the siliconizing treatment is performed in an atmosphere of various oxygen equivalents [O].

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

Front Page Continuation (72) Inventor Kazuhisa Okada Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Tube Co., Ltd. (72) Inventor Hironori Ninomiya 1-2 Marunouchi Marunouchi, Tokyo Nihonkansen Stock In the company

Claims (3)

[Claims] 1. A steel sheet containing Si: less than 4 wt%,
A high silicon steel sheet is obtained by performing a siliconizing treatment in a non-oxidizing gas atmosphere containing SiCl ₄ in the siliconizing zone and then performing a diffusion heat treatment for diffusing Si into the steel sheet in an non-oxidizing gas atmosphere containing no SiCl _4. In the method for continuously producing, a steel sheet containing carbon in an amount satisfying the following formula is used as a base steel sheet to be subjected to siliconizing treatment, according to the atmosphere in the siliconized zone in the furnace. A method for manufacturing a high silicon steel sheet having excellent surface properties. 0.2 [O] −27 ≦ [C] ≦ 0.3 [O] +116, where [O]: oxygen equivalent (ppm) in the furnace atmosphere [C]: carbon content (ppm) of the base steel sheet 2. A steel sheet containing Si: less than 4 wt%,
A high silicon steel sheet is obtained by performing a siliconizing treatment in a non-oxidizing gas atmosphere containing SiCl ₄ in the siliconizing zone and then performing a diffusion heat treatment for diffusing Si into the steel sheet in an non-oxidizing gas atmosphere containing no SiCl _4. In the method for continuously producing, a steel sheet containing carbon in an amount satisfying the following formula is used as a base steel sheet to be subjected to siliconizing treatment, according to the atmosphere in the siliconized zone in the furnace. A method for manufacturing a high silicon steel sheet having excellent surface properties. 0.2 [O] −27 ≦ [C] ≦ 0.3 [O] +66, where [O]: oxygen equivalent (ppm) in the furnace atmosphere [C]: carbon content (ppm) of the base steel sheet 3. A steel sheet containing Si: less than 4 wt%,
A high silicon steel sheet is obtained by performing a siliconizing treatment in a non-oxidizing gas atmosphere containing SiCl ₄ in the siliconizing zone and then performing a diffusion heat treatment for diffusing Si into the steel sheet in an non-oxidizing gas atmosphere containing no SiCl _4. In the method for continuously producing, a steel sheet containing carbon in an amount satisfying the following formula is used as a base steel sheet to be subjected to siliconizing treatment, according to the atmosphere in the siliconized zone in the furnace. A method for manufacturing a high silicon steel sheet having excellent surface properties. 0.2 [O] + 5 ≦ [C] ≦ 0.3 [O] +66, where [O]: oxygen equivalent (ppm) in furnace atmosphere [C]: carbon content (ppm) of base steel sheet