JPH09176826A - Continuous production of high silicon steel sheet excellent in surface property and good in workability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of pickup caused by the formation of silica by suppressing the formation of silica in a siliconizing zone. SOLUTION: A steel sheet contg. <4wt.% Si is subjected to siliconizing treatment in a nonoxidizing gaseous atmosphere in a siliconizing zone and is next subjected to diffusion soaking treatment of diffusing Si over the inside part of the steel sheet in a diffusion soaking zone to continuously produce a high silicon steel sheet. Then, the steel sheet before being applied with the siliconizing treatment is subjected to decarburizing treatment to increase the content of carbon in the steel sheet, and after that, the siliconizing treatment and subsequent diffusion soaking treatment are executed, and in the carburizing treatment and diffusion soaking treatment, by the oxygen content in the atmosphere in the furnace, decarburizing reaction is allowed to occur in the steel sheet. By this decarburizing reaction, the oxygen content in the furnace is consumed, by which, while the formation of silica is prevented, the high silicon steel sheet having <=60ppm car on content can be produced.

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 continuous 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, etc., a steel sheet is subjected to continuous siliconizing treatment at a temperature of 1023 ° C. to 1200 ° C. in a non-oxidizing gas atmosphere containing ₅ to 35 wt% of SiCl ₄ to form a coil. Of 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 line is equipped with a heating zone, a siliconizing zone, a diffusion soaking zone and a cooling zone from the inlet side. After continuously heating the steel sheet to the processing temperature in the heating zone, the SiCl ₄ zone is used in the siliconizing zone. Si is infiltrated by reacting with, and then a heat treatment for diffusing Si in the plate thickness direction is continuously performed in the diffusion soaking zone, and the coil-shaped high silicon steel sheet is obtained by cooling in the cooling zone. Manufactured.

[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 generated in the surface of the steel sheet by the reaction of SiCl ₄ with a trace amount of oxygen and moisture in the atmosphere in the siliconized zone is We have found out that it is the source of the flaw.

That is, a large amount of reaction gas SiCl ₄ is supplied to the siliconizing 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

When such silica is generated on the surface of the steel sheet and adheres to the surface of the steel sheet, the silica is transferred and deposited on the surface of the hearth roll for conveying the steel sheet installed in the furnace, so that the surface of the hearth roll becomes uneven. It was found that the unevenness caused dents on the steel sheet heated to a high temperature (this phenomenon is called pickup). Therefore, as a measure to suppress the formation of such silica,
It is conceivable to control the atmosphere so as to reduce the oxygen concentration and the dew point in the atmosphere in the siliconizing zone. However, it is technically extremely difficult to lower the oxygen concentration and dew point in the furnace in a continuous furnace, and it takes a very long time to lower the dew point and oxygen concentration to a certain level.

Particularly, since the inside of the siliconizing zone of the continuous siliconizing line is a special environment in which the above-mentioned siliconizing reaction occurs, it is much more difficult to control the atmosphere in the furnace as compared with a general continuous annealing line. . In addition, recently, the use ratio of fiber-based refractory materials having excellent heat insulation properties as furnace refractory materials has been increasing, and since this fiber-based refractory material has a high porosity, H ₂ O
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 such refractory material gradually leach into the atmosphere in the furnace during the operation, which makes it extremely difficult to control the atmosphere in the siliconizing zone. Therefore, it is not easy to control the atmosphere in the furnace in practice, and even if such a low dew point and low oxygen concentration could be achieved at the beginning of the operation of the furnace, the dew point and the oxygen concentration would be reduced if the operation was continued for a certain period of time. It rises and picks up.

Therefore, an object of the present invention is to suppress the generation of silica in the siliconized zone without strict control and control of the dew point and oxygen concentration of the furnace atmosphere of the siliconized zone and to form the silica. It is an object of the present invention to provide a method capable of appropriately preventing the occurrence of pickup due to the above and stably manufacturing a high-silicon steel sheet having excellent surface properties.

[0010]

In order to solve such problems, the present invention has the following features. [1] Si: A steel sheet containing less than 4 wt% is subjected to a siliconizing treatment in a non-oxidizing gas atmosphere containing SiCl ₄ in the siliconizing treatment zone, and then an nonoxidizing gas containing no SiCl ₄ in the diffusion soaking zone. In a method for continuously producing a high-silicon steel sheet by performing a diffusion soaking treatment for diffusing Si into the steel sheet in an atmosphere, a carbon content in the steel sheet is obtained by carburizing the steel sheet before the siliconizing treatment. After increasing the amount, the siliconizing treatment and the subsequent diffusion soaking treatment are performed, and the decarburization reaction of the steel sheet is caused by the oxygen content in the furnace atmosphere in the siliconizing treatment and the diffusion soaking treatment, whereby the diffusion A continuous production method of a high silicon steel sheet having excellent surface properties and good workability, characterized by obtaining a high silicon steel sheet having a carbon content of 60 ppm or less after soaking.

[2] In the manufacturing method of the above-mentioned [1], the carburizing treatment is carried out by gas carburizing or solid carburizing in a heating zone provided immediately before the siliconizing zone. A good continuous production method of a high silicon steel sheet.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the reaction in which silica, which causes the occurrence of flaws in the steel sheet, occurs in the siliconizing zone is basically the oxygen and moisture in the atmosphere on the surface of the steel sheet. And S
It is a reaction that reacts with iCl ₄ to generate silica on the surface of the steel sheet. Therefore, a reducing agent that consumes oxygen and moisture (oxygen source) in the atmosphere on the surface of the steel sheet, which is also SiCl
If there is a reducing agent that has a higher reducing ability compared to ₄ ,
The oxygen source in the atmosphere is consumed by the reaction with the reducing agent, and S
It no longer reacts with iCl ₄ . On the other hand, however, the reducing agent should not affect the properties of the steel sheet itself or the siliconizing treatment.

In the present invention, attention is paid to carbon contained in the steel sheet as a reducing agent suitable for obtaining the above-mentioned action. That is, carbon exhibits an extremely high reducing ability in a high temperature atmosphere such as a siliconized zone, and carbon contained in a steel sheet reacts with moisture and oxygen in the atmosphere present on the surface of the steel sheet to form CO (gas). To generate. That is, the decarburization reaction of the steel sheet consumes oxygen and water on the surface of the steel strip. As a result, SiCl
No. ₄ loses the oxygen source to react on the surface of the steel sheet and prevents the formation of silica. Further, even if a large amount of carbon is contained in the steel sheet in advance in order to obtain the above reaction, this carbon does not react with the above decarburization reaction in the siliconizing zone, and further the decarburization reaction in the subsequent diffusion soaking zone. (Since it reacts with oxygen in the atmosphere on the surface of the steel strip and the reaction of carbon in the steel strip with carbon in the steel strip as in the case of the siliconizing treatment zone), CO is released from the steel sheet. If the control is carried out within an appropriate range according to the decarburization amount, carbon will not remain excessively in the steel sheet and will not adversely affect the magnetic properties and the like of the produced high silicon steel sheet. Therefore, by adding an appropriate amount of carbon to the steel sheet before the siliconizing treatment, it does not adversely affect the magnetic properties of the product steel strip (high silicon steel strip) and the like on the steel strip surface during the siliconizing treatment. It is possible to appropriately prevent the generation of silica.

By the way, as a method for adding a large amount of carbon to the steel sheet before the siliconizing treatment, it is conceivable to adjust a large amount of carbon in the steel at the steel making stage. However, when a large amount of carbon is contained in the steel in the steelmaking stage, there is a problem that the rolling property and the weldability are significantly deteriorated such that the steel plate is broken during rolling or cracks or welding defects are likely to occur during coil welding. Further, as a problem before that, it is difficult to control the carbon content within the limited range required by the method of the present invention in the steelmaking stage. That is, if the carbon content in the base steel sheet is too high, the siliconizing treatment-
Since the residual carbon amount after the diffusion soaking is excessive, the iron loss characteristics and the like of the produced high-silicon steel sheet are significantly deteriorated, while if the carbon content in the base steel sheet is too small, the above reaction is effective. It is not possible to appropriately suppress the generation of silica on the steel strip surface because it does not occur, and therefore the carbon content of the base steel sheet must be controlled to a specific range with high accuracy. It is difficult to precisely control the amount of carbon. In addition, the appropriate carbon content in the steel sheet before the siliconizing treatment is always constant because it changes depending on the reaction amount in the siliconizing treatment zone and the diffusion soaking zone, in other words, the oxygen concentration and dew point in the atmosphere of those zones. This is not the case, and it is virtually impossible to deal with such changes in the proper carbon content by the method of adjusting the carbon content in the steelmaking stage.

Therefore, the present inventors set the carbon content in the base steel sheet within a desired range according to the oxygen concentration in the furnace atmosphere and the dew point without impairing the rolling property and weldability of the base steel sheet. As a result, it was concluded that the method of continuously carburizing the steel sheet in the heating stage before the siliconizing treatment is the most suitable. That is, if carbon is added to the base steel sheet by such a method, the rollability and weldability of the steel sheet are not a problem at all, and the atmosphere in the furnace such as the siliconized zone and the thickness of the steel sheet to be treated, the steel sheet The amount of carbon added can be easily controlled regardless of the in-furnace time, and the amount of carbon added can be changed at any time. Therefore, if the steel sheet having the carbon content appropriately controlled in this manner is subjected to the siliconizing treatment, the generation of silica on the steel sheet surface is appropriately prevented by the decarburization reaction, and moreover the obtained high silicon steel sheet has an excessive amount. No carbon remains.

The above-mentioned carburizing treatment is carried out in the heating stage immediately before the base material steel plate is subjected to the siliconizing treatment, and in the usual continuous siliconizing treatment line (see FIG. 3), the heating zone exists immediately before the siliconizing treatment zone. Usually, carburization is performed in this heating zone. Hereinafter, the case where the carburizing process is performed in this heating zone will be described as an example.
Although the method of carburizing treatment in the heating zone is arbitrary, it is usually carried out by a gas carburizing method or a solid carburizing method.
Among them, the gas carburizing method is carried out by setting a carburizing gas atmosphere in the heating zone or by blowing an atmosphere gas for blowing the carburizing gas in the heating zone onto the steel plate surface. Usually, CO, CH ₃ or the like can be used as the carburizing gas, and an atmosphere gas containing these carburizing gases (for example, CO—N ₂ atmosphere gas, CH ₃ —N ₂ atmosphere gas) is used. The carburizing amount can be arbitrarily adjusted by controlling the carburizing gas concentration in the atmosphere gas and / or the dew point in the furnace.

When a gas containing hydrogen such as CH ₃ is used as the carburizing gas, H ₂ is generated by the carburizing reaction. Therefore, the atmosphere gas in the heating zone containing H ₂ enters the siliconizing zone. It is necessary to devise something that does not happen. The reason for this is that, when H ₂ enters the siliconized zone, it reacts with SiCl ₄ to generate hydrochloric acid, which etches the steel sheet or precipitates metal Si and deteriorates the properties of the steel sheet surface. . Therefore, CO is more preferable as the carburizing gas because such consideration is unnecessary.

The solid carburizing method can be carried out, for example, by applying carbon particles or carbon-containing particles to the surface of the steel sheet before the steel sheet enters the heating zone, and the amount of carburizing can be controlled by controlling the application amount of carbon particles or the like. Can be adjusted by. As a specific coating method, the carbon particles or the like may be directly applied to the surface of the steel plate by coating, or the carbon particles or the like may be dispersed in an appropriate solvent (for example, a volatile organic solvent), and then the steel plate surface Alternatively, it may be applied by a coating device or the like. In the latter case, the coating film may be dried to form a carbon film (or a carbon-containing film) and then introduced into the heating zone. In such a solid carburizing method, the carburizing amount can be directly controlled by the coating amount, and thus there is an advantage that the carburizing amount can be easily controlled.

Using a batch type test furnace, the carbon content is 20
After carburizing a 3 ppm Si steel sheet of ppm by a gas carburizing method, a carburizing treatment is performed so that the average Si content in the plate thickness direction is 6.
A 5% high silicon steel sheet was manufactured, and the relationship between the carbon content of the steel sheet after the carburizing treatment and the amount of silica generated on the steel sheet surface by the siliconizing treatment was investigated. The result is shown in FIG. In this test, at 2 minutes steel in CO-N ₂ atmosphere 12
After raising the temperature to 00 ° C., it was held for 1 minute to carry out a carburizing treatment, and after cooling, the carbon content of the steel sheet was measured. In this carburizing process, the CO concentration in the atmosphere is 0.01-
The amount of carburization was adjusted by changing it in the range of 0.6%.
Then, the carburized steel sheet is reheated, and then a siliconizing gas atmosphere (SiCl ₄ concentration: 20 vol%, balance:
In N ₂ ) while keeping the dew point at -30 ° C.
Silicidation treatment was performed at 0 ° C. for 3 minutes, and the amount of silica adhering to the treated steel plate surface was measured. According to Fig. 1, when the steel sheet subjected to the carburizing treatment to increase the carbon content before the siliconizing treatment has undergone the siliconizing treatment, the amount of generated silica is significantly larger than that of the steel sheet subjected to the siliconizing treatment without the carburizing treatment. It has been decreased, and it can be seen that as a result of the above-described decarburization reaction of the steel sheet, the silica generation reaction during the siliconizing treatment is suppressed.

The minimum carburizing amount required to prevent silica from forming on the steel strip surface in the siliconizing zone depends on the original carbon content of the base steel sheet and the oxygen concentration and dew point in the atmosphere of the siliconizing zone. It will be decided. On the other hand, if the amount of carburization of the base steel sheet is excessive, the effect of suppressing silica generation can be obtained without any problem, but excess carbon remains in the product steel sheet after the siliconizing treatment and diffusion soaking treatment, and the magnetic properties of the product steel sheet Significantly deteriorates. FIG. 2 shows the relationship between the carbon content and the iron loss value in a high silicon steel sheet (6.5% Si steel sheet). The iron loss value starts to increase when the carbon amount in the steel sheet exceeds 50 ppm, 60
Above ppm, it increases sharply. Therefore, the amount of carburizing the base steel sheet should be suppressed to an amount such that the carbon content of the steel sheet does not exceed 60 ppm at the time when the siliconizing treatment and the soaking diffusion treatment are completed.

The decarburization amount during the siliconizing treatment and the diffusion soaking treatment is determined by the dew point in the atmosphere in the furnace, the oxygen concentration and the processing time (the time spent in the furnace in each processing zone). It is necessary to control the amount of carburization in the heating zone according to the oxygen concentration, the treatment time (further, the thickness of the steel sheet to be treated, if necessary), and the like. Therefore, for example, by feeding back the above parameters (dew point and oxygen concentration in the siliconizing zone and diffusion soaking zone, treatment time, etc.) to the carburizing amount control in the heating zone, the carbon content of the final product is reduced to 60 ppm or less. It is preferable to control. As described above, the amount of carburization in the heating zone can be controlled by controlling the concentration of carburizing gas in the case of gas carburizing, for example.

When the carbon content of the steel sheet is less than 10 ppm, the ability to consume moisture and oxygen in the atmosphere is almost lost, so that the carbon content of the steel sheet becomes less than 10 ppm at the end of the diffusion soaking treatment. If so, there is a possibility that silica may be generated in the furnace or grain boundary oxidation described later may occur. On the other hand, 10
If carbon content of more than ppm remains, the steel sheet will come out of the furnace in a state where the surplus capacity of reacting with moisture and oxygen is still maintained, and there is no possibility of causing the above-mentioned problems. Therefore, the carbon content of the steel sheet is preferably 10 ppm or more when the diffusion soaking treatment is completed.

Further, by adding carbon to the steel strip by the carburizing treatment, the steel sheet surface and grain boundary oxidation in the furnace (siliconizing treatment zone and diffusion soaking zone) are effectively prevented,
As a result, it was found that the workability was also improved as compared with the high silicon steel strip produced without carburizing. Similar to the effect of suppressing the generation reaction of silica, such an antioxidant effect suppresses the oxidation reaction of steel as a result of the oxygen and water present in the atmosphere gas on the surface of the steel sheet being consumed in the decarburization reaction. It is due to being done. Therefore, the oxidation of the steel strip, which is one of the causes of the poor workability of the high silicon steel strip, particularly the grain boundary oxidation, is appropriately suppressed, and the workability for bending and the like is improved.

In the production of a high silicon steel sheet by the continuous siliconizing method, which is the object of the present invention, the siliconizing zone is usually made of Si.
A processing gas having a Cl ₄ concentration of about 5 to 35 mol% was supplied, and the steel plates introduced into this siliconized zone were 1023 to 1
It is subjected to a siliconizing treatment at a treatment temperature of about 200 ° C., subsequently introduced into a diffusion soaking zone, and soaked at a treatment degree of about 1200 to 1230 ° C. The silicon content of the high silicon steel sheet produced is arbitrary, but generally Si: 5-10
A wt% high silicon steel sheet is manufactured.

[0025]

【Example】

[Example 1] In the continuous siliconizing treatment line shown in FIG.
A 3% Si steel plate having a carbon content of 20 ppm and a plate thickness of 0.3 mm was subjected to continuous siliconizing treatment to produce a 6.5% Si steel plate. At this time, in the example of the present invention, gas carburization was performed in the heating zone, while in the comparative example, gas carburization was not performed. In the example of the present invention in which the carburizing treatment was performed in the heating zone, 0.6% CO
The steel sheet was heated to 1200 ° C. in a −N ₂ gas atmosphere. The in-furnace time within the heating zone of the steel sheet at this time was 6 minutes. Further, the conditions of the siliconizing treatment and the diffusion soaking treatment are as follows in the present invention example and the comparative example.

(A) Siliconization treatment conditions Atmosphere conditions in furnace Atmosphere gas: N ₂ + SiCl ₄ (concentration 18 vol%) Dew point: -30 ° C. Treatment temperature: 1200 ° C. Treatment time (Steel strip working time): 5 minutes ( b) Diffusion soaking condition In-furnace atmosphere condition Atmospheric gas: N ₂ Dew point: -50 ° C Treatment temperature: 1200 ° C Treatment time (Steel band working time): 15 minutes

With respect to the manufactured 6.5% Si steel sheet, the amount of silica adhering to the steel sheet surface was measured, and the workability of the steel sheet was evaluated by measuring the critical bending radius. The results are shown in FIGS. As is clear from these, in the examples of the present invention in which gas carburization was carried out in the heating zone, almost no silica was generated, and the workability of the produced high-silicon steel sheet was good. In addition, Table 1 shows the analysis value of the residual carbon amount and the iron loss value of the manufactured high silicon steel sheet. According to this, the high silicon steel sheet obtained in the example of the present invention also has a carbon content of 60 ppm or less, and therefore the iron loss value is also good.

[0028]

[Table 1]

Example 2 In the continuous siliconizing treatment line shown in FIG. 3, a 3% Si steel plate having a carbon content of 20 ppm and a plate thickness of 0.3 mm was continuously siliconized to produce a 6.5% Si steel plate. . At this time, a carbon film for solid carburization was partially formed on the steel sheet before being introduced into the heating zone, the part on which the carbon film was formed was set as an example of the present invention, and the part on which the carbon film was not formed was set as a comparative example. In the portion of the present invention example, a carbon film was formed by applying an organic solvent (toluene and methyl alcohol) in which carbon particles were dispersed onto the steel plate surface before introducing it into the heating zone and drying it. The siliconizing treatment conditions and the diffusion soaking treatment conditions are as follows.

(A) Siliconization treatment conditions In-furnace atmosphere conditions Atmosphere gas: N ₂ + SiCl ₄ (concentration 18 vol%) Dew point: -30 ° C. Treatment temperature: 1200 ° C. Treatment time (Steel strip working time): 5 minutes ( b) Diffusion soaking condition In-furnace atmosphere condition Atmospheric gas: N ₂ Dew point: -50 ° C Treatment temperature: 1200 ° C Treatment time (Steel band working time): 15 minutes

When the generation conditions of silica were compared between the produced inventive 6.5% Si steel sheet and the comparative example, the white powdery silica adhered to the entire surface of the comparative example. However, silica was not attached to the carburized portion of the present invention, and the steel strip surface was very glossy. In addition, regarding the portion of the present invention example and the portion of the comparative example, the amount of silica adhering to the steel sheet surface was measured, and the workability of the steel sheet was evaluated by measuring the critical bending radius. The results are shown in FIGS. As is clear from these, even in the case of the present invention in which the solid carburization was carried out, almost no silica was generated, and the workability of the produced high silicon steel sheet was good.

[0032]

According to the present invention described above, in the method for producing a high silicon steel sheet by the continuous siliconizing treatment method, the steel sheet during the siliconizing treatment is not deteriorated without deteriorating the magnetic characteristics of the produced high silicon steel sheet. It is possible to appropriately prevent the generation of silica on the surface, and also to suppress the oxidation on the steel sheet surface and grain boundaries during the siliconizing treatment and the diffusion soaking treatment,
For this reason, it is possible to stably manufacture a high silicon steel sheet having excellent surface properties without dents and the like and having good workability and magnetic properties. Further, since carbon is added to the steel strip by utilizing the heating step immediately before the siliconizing treatment, the amount of carbon added can be easily adjusted according to the atmosphere in the furnace.

[Brief description of the drawings]

FIG. 1 A 3% Si steel sheet having a carbon content of 20 ppm is carburized by a gas carburizing method and then subjected to a silicon carburizing treatment to 6.5.
A graph showing the relationship between the carbon content of the steel sheet after the carburizing treatment and the amount of silica generated on the steel sheet surface by the carburizing treatment when the% Si steel sheet was manufactured.

FIG. 2 is a graph showing the relationship between carbon content and iron loss value in a high silicon steel sheet (6.5% Si steel sheet).

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

FIG. 4 is a graph showing the amount of silica adhering to the steel plate surface for the 6.5% Si steel plates of the present invention example and comparative example manufactured in Example 1.

FIG. 5 is a graph showing the machinability of the 6.5% Si steel sheets of the present invention and the comparative example produced in Example 1 evaluated by the limit bending radius of the steel sheet.

FIG. 6 is a graph showing the amount of silica adhering to the steel plate surface for the 6.5% Si steel plates of the present invention example and comparative example manufactured in Example 2;

FIG. 7 is a graph showing the workability of the 6.5% Si steel sheets of the present invention example and the comparative example produced in Example 2 evaluated by the critical bending radius of the steel sheet.

Claims (2)

[Claims] 1. A steel sheet containing Si: less than 4 wt%,
The siliconizing treatment is performed in a non-oxidizing gas atmosphere containing SiCl ₄ in the siliconizing treatment zone, and then Si is applied in the diffusion soaking zone.
In a method for continuously producing a high-silicon steel sheet by performing a diffusion soaking treatment for diffusing Si into the steel sheet in a non-oxidizing gas atmosphere containing no Cl ₄ , a carburizing treatment is performed on the steel sheet before the siliconizing treatment. To increase the carbon content in the steel sheet, the siliconizing treatment and the subsequent diffusion soaking treatment are performed, and the steel sheet is deoxidized by the oxygen content in the furnace atmosphere in the siliconizing treatment and the diffusion soaking treatment. By causing a charcoal reaction, the carbon content after diffusion soaking is 60 p
A continuous production method of a high silicon steel sheet having excellent surface properties and good workability, characterized by obtaining a high silicon steel sheet of pm or less. 2. The high silicon having excellent surface properties and good workability according to claim 1, wherein the carburizing is performed by gas carburizing or solid carburizing in a heating zone provided immediately before the siliconizing zone. Continuous manufacturing method of steel sheet.