JPH0643610B2 - Method for producing high silicon steel strip in continuous line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to chemical vapor deposition in a continuous line (hereinafter referred to as C
The present invention relates to a method for producing a high silicon steel strip by the VD method).

[Conventional technology]

A high silicon steel plate is used as the electromagnetic steel plate. With this type of steel sheet, iron loss is reduced as the Si content increases, and Si:
It is known that at 6.5%, the magnetostriction becomes 0, and the maximum magnetic permeability reaches a peak, exhibiting the best magnetic properties.

Conventionally, there are a rolling method, a direct casting method and a siliconizing method as a method for producing a high silicon steel sheet. Among them, the rolling method can produce a Si content of up to about 4%.
Cold working is difficult because the workability is remarkably deteriorated with the content. Further, the direct casting method, so-called strip casting, does not cause the problem of workability as in the rolling method, but it is still under development, and it is easy to cause shape defects, and it is particularly difficult to manufacture high silicon steel sheets. is there.

On the other hand, the siliconizing method produces a high silicon steel sheet by melting low silicon steel and rolling it into a thin plate, and then infiltrating Si from the surface. A high silicon steel plate can be obtained without causing any problems.

[Problems to be solved by the invention]

This siliconization method was proposed by Gokyu and Abe, and was examined in detail by Mitani and Onishi. However, all of the conventionally proposed methods have a long infiltration treatment time of 30 minutes or more, and after the CVD treatment. The diffusion heat treatment that is carried out is
There is a fundamental problem that it takes a relatively long time because it is necessary to uniformly disperse the metal in the base metal, and it cannot be applied to a continuous line in practice. Further, since the CVD treatment temperature is also extremely high at about 1230 ° C., the shape of the thin steel sheet after the infiltration treatment is extremely poor, and the treatment temperature is too high, so that the edge portion may be melted by overheating. I can't expect a stable threading.

Further, in the siliconizing method, Fe on the surface of the steel plate becomes FeCl ₂ due to the vapor deposition reaction.
And the like, which reduces the plate pressure. However, in this type of treatment, the deposition (film thickness) is likely to be non-uniform due to the non-uniformity of the atmospheric gas concentration distribution, etc. As a result, there is variation in how the plate thickness decreases, and the plate thickness varies in the width direction and the longitudinal direction. However, there is a problem in that it tends to be non-uniform.

In addition, a high silicon steel sheet having a Si content of 4.0% or more is brittle, and there is a problem that the steel sheet after processing is easily broken when wound into a coil.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and is a method capable of stably producing a high-quality high-silicon steel strip in a continuous line in a short time in a continuous line by using a siliconizing method. For the purpose of providing.

[Means for solving problems]

Therefore, according to the present invention, while continuously passing the steel strip in an atmosphere of non-oxidizing gas, SiCl ₄ is used in a mol ratio of 5 to 35%.
The contained non-oxidizing gas is sprayed from the spray nozzle onto the steel strip surface to continuously perform the silicidation treatment at a temperature of 1023 to 1200 ° C.
Then, S in a non-oxidizing gas atmosphere containing no SiCl ₄
When performing the diffusion treatment for diffusing i into the steel strip, the diffusion treatment was terminated while the surface layer Si concentration was higher than the Si concentration in the central portion in the thickness direction of the steel strip, and the Si concentration was uneven in the thickness direction. The basic feature is that a steel strip is obtained, and the steel strip is plastically worked by rolling at 200 to 600 ° C. during or after the subsequent cooling process.

Another basic feature of the present invention is that after the plastic processing by the diffusion treatment-cooling and rolling, an insulating film coating is applied and then a baking treatment is performed.

Hereinafter, the details of the present invention will be described.

In the present invention, the composition of the steel strip (starting thin steel strip) as the base material is not particularly limited, but it is preferably determined as follows in order to obtain excellent magnetic properties.

In the case of 3 to 6.5% Si-Fe alloy C: 0.01% or less, Si: 0 to 4.0%, Mn: 2% or less,
It is desirable that other unavoidable impurities be as low as possible.

In the case of Sendust alloy C: 0.01% or less, Si: 4% or less, Al: 3-8%, N
It is desirable that i: 4% or less, Mn: 2% or less, elements such as Cr and Ti that increase corrosion resistance of 5% or less, and other unavoidable impurities as low as possible.

The steel strip is not limited to that obtained by hot rolling-cold rolling, but may be obtained by direct casting or rapid solidification.

As described above, the steel strip has a reduced plate thickness due to the CVD process, and therefore, it is necessary to use a plate having a thickness reduced by the final product plate thickness.

According to the present invention, such a steel strip is subjected to a siliconizing treatment by a CVD method.
A high silicon steel strip is obtained by applying a diffusion treatment.

FIG. 1 shows a continuous processing line for carrying out the method of the present invention. (1) is a heating furnace, (2) is a CVD processing furnace, (3) is a diffusion processing furnace, and (4) is a cooling furnace. is there.

The steel strip (S) is non-oxidatively heated up to or near the CVD processing temperature in the heating furnace (1), and then introduced into the CVD processing furnace (2), where S
Silicidation is performed by a CVD method in an atmosphere of non-oxidizing gas containing iCl ₄ . The non-oxidizing gas containing SiCl ₄ means a neutral or reducing gas, and as the carrier gas of SiCl ₄ , Ar, H ₂ , He, H ₂ , CH ₄ or the like can be used. Among these carrier gases, when considering the processability of exhaust gas, H ₂ , CH _{4 and the} like generate HCl, which has a disadvantage that the process is required, and Ar, He, and N ₂ that do not cause such a problem are generated. Of these, Ar and He are most preferable from the standpoint of difficulty in preventing nitriding of the material.

The main reaction of the steel strip surface in the CVD treatment is 5Fe + SiCl ₄ → Fe ₃ Si + 2FeCl ₂ ↑ Si1 atoms are vapor-deposited on the steel strip surface to form a Fe ₃ Si layer, and Fe ₂ atoms become FeCl ₂ and FeCl ₂ Boiling point 1023 ° C
At the above temperatures, it is emitted from the surface of the steel strip in a gaseous state. Therefore, Si atomic weight is 28.086 and Fe atomic weight is 5
Since it is 5.847, the mass of the steel strip decreases, and the plate thickness also decreases accordingly. By the way, if Si3% steel strip is used as the base material and Si6.5% steel strip is manufactured by CVD treatment,
The mass is reduced by 8.7% and the plate thickness is reduced by about 7.1%.

In the conventional method, the CVD process takes too long,
It is considered that this is because the CVD processing conditions have not been sufficiently studied. The inventors of the present invention have studied and found that there are the following elements for rapid CVD processing.

Optimization of SiCl ₄ concentration in the gas in the atmosphere.

Optimization of processing temperature.

Promotion of diffusion of SiCl _{4 to} the steel strip surface and emission of FeCl _{2 from} the steel strip surface.

Therefore, in the present invention, the Si concentration in the atmospheric gas and the processing temperature in the CVD processing are defined.

First, SiCl in a non-oxidizing gas atmosphere in the CVD process
₄ concentration mol fraction is defined to be 5 to 35%, and the steel strip is subjected to continuous CVD treatment in such an atmosphere.

The effect of Si enrichment expected to be less than 5% of SiCl ₄ in the atmosphere cannot be obtained, and it takes more than 5 minutes to enrich Si of the steel strip by 1.0%. It takes too much time, and it becomes difficult to form a continuous process.

On the other hand, even if SiCl ₄ is contained in an amount of more than 35%, the reaction at the interface becomes rate-determining and further Si enrichment effect cannot be expected.

Moreover, in the CVD process, the higher the SiCl ₄ concentration, the more easily large voids called so-called Kirkendall voids are generated. This void is hardly seen up to a SiCl ₄ concentration of about 15%, but begins to form when it exceeds 15%. But,
If the SiCl ₄ concentration is 35% or less, CV
It can be almost completely eliminated by the diffusion process performed after the D process. The time required for the voids to disappear depends strongly on the diffusion treatment temperature, and the surface layer
Voids can be eliminated in a short time by raising the treatment temperature according to the decrease in Si concentration. However, when the SiCl ₄ concentration exceeds 35%, the diameter of the generated voids becomes large, and adjacent voids coalesce to become even larger, and the voids remain even after the diffusion and soaking treatment for a long time. In contrast, the SiCl ₄ concentration is 35%
If it is below, it does not become a very large void and can be eliminated by diffusion processing.

The CVD processing temperature is in the range of 1023 to 1200 ° C.
Since the CVD treatment reaction is a reaction on the surface of the steel strip, this treatment temperature is strictly the surface temperature of the steel strip.

The boiling point of FeCl ₂ which is a reaction product of the CVD process is 10
The temperature is 23 ° C., and below this temperature, FeCl ₂ is not diffused from the surface of the steel strip in a gaseous state, and adheres to the surface of the steel strip in a liquid state to hinder the vapor deposition reaction. The results of basic experiments conducted by the present inventors show that the enrichment ratio of Si per unit time is remarkably different at the boiling point of FeCl ₂ as a boundary, and if the temperature is less than 1023 ° C., the vapor deposition rate is small and thus it is difficult to apply to a continuous process. Is. Therefore, the lower limit of the processing temperature is 1023 ° C.

On the other hand, the reason for defining the upper limit as 1200 ° C. is as follows. The melting point of Fe ₃ Si is 1250 ° C. as is clear from the Fe-Si phase diagram shown in FIG. 4, but according to the experiments by the inventors, even when treated at about 1230 ° C. lower than 1250 ° C., The surface of the steel strip is partially melted, and the edge portion of the steel strip is melted due to overheating. 1250 like this
It is presumed that the reason why the steel strip melts even at a temperature equal to or lower than ° C is that Si is vapor-deposited on the surface of the steel strip at a Si concentration of 14.5% or more corresponding to Fe ₃ Si. In contrast, the processing temperature is 1200
If the temperature is below ℃, no melting is observed on the surface of the steel strip, and even if the edge is overheated, the average temperature of the central portion of the steel strip is 120
By setting the temperature to 0 ° C., it was possible to suppress the temperature to about 1220 ° C., and it was experimentally confirmed that a minute amount of dissolution was sufficient. For the above reasons, the CVD processing temperature is 1023 ° C to 1
It is specified as 200 ° C.

In order to increase the CVD processing rate to the extent that continuous processing of steel strip is possible, SiCl ₄ in the atmosphere gas as described above can be used.
It is necessary to optimize the concentration and treatment temperature, but in addition to this, supply and diffusion of SiCl ₄ to the steel strip surface and promotion (release) of FeCl _{2 as} a reaction byproduct from the steel strip surface are promoted. Therefore, it is necessary to further increase the CVD processing speed.

In the past, when a reaction gas was largely flowed in the CVD process, voids were generated in the vapor deposition layer and the purity of the vapor deposition layer was also lowered. Therefore, the idea that the gas flow should be kept to the minimum necessary was established. However, in the study by the present inventors, by suppressing the gas flow in this way, the diffusion transfer of the reaction gas to the base material interface and the separation of the reaction by-product from the interface surface layer are not smoothly performed, and therefore, It has been found that the processing requires a long time, and further, the gas flow is suppressed, so that the reaction gas concentration in the CVD processing furnace is distributed, and as a result, the deposition film thickness becomes nonuniform.

As a result of further study based on such facts, by spraying an atmosphere gas onto a material to be processed by a spray nozzle in a CVD processing furnace, diffusion of SiCl ₄ to the surface of the steel strip and reaction product FeCl ₂ of It was found that the CVD process can be carried out at a high vapor deposition rate while suppressing the non-uniformity of the vapor deposited film by significantly promoting the emission from the surface of the steel strip.

Most of what is generally called a CVD reaction is that which is produced (deposited) by the reaction of gas in the gas phase and adheres to the substrate surface. By-products (reaction product gas) in the case of this reaction Occurs in the gas phase and is not generated from the solid side. On the other hand, in the siliconizing treatment of the steel strip, Fe is replaced with Si in the reaction gas on the surface of the steel strip, so that Si is taken into the steel. This is called a substitutional CVD reaction, and FeCl ₂ is generated as a gas (reaction product gas) from the surface of the steel strip, that is, the solid side. Therefore, in a process involving such a substitutional CVD reaction, the reaction product gas is generated from the solid side, which is a generally known CVD method.
The behavior of the reaction product gas different from the reaction is shown.

In such a substitutional CVD reaction, the reaction is promoted by supplying the atmospheric gas containing the reaction gas to the surface of the steel strip one after another and promptly releasing the reaction product gas (FeCl ₂ ) from the reaction interface. Extremely important above.

In this sense, spraying the atmospheric gas onto the steel strip surface with a spray nozzle has a great advantage that the reaction gas can be supplied to the reaction interface and the separation of the reaction product gas from the reaction interface can be promoted.

FIG. 6 shows a state of implementation by this nozzle spraying method. A spray nozzle 5 is arranged in the CVD treatment furnace 2 so as to face the steel strip S, and an atmosphere gas containing SiCl ₄ is sprayed on the surface of the steel strip. 7 (a) and 7 (b) show the spraying situation by the spraying nozzle. As shown in FIG. 7 (a), it is from the direction perpendicular to the steel strip surface or diagonally as shown in (b). Gas can be sprayed from the direction.

The Si enrichment rate per unit time due to such nozzle spraying increases in proportion to the increase in the collision flow velocity of the gas with respect to the steel strip surface, but even if the flow velocity is excessively increased, the reaction rate is limited at the interface. The above Si enrichment effect cannot be expected. Generally, a sufficient effect can be obtained at a flow velocity of 5 Nm / sec or less.

The steel strip (S) subjected to the CVD treatment as described above is continuously introduced into the diffusion furnace (3) and subjected to the diffusion treatment in the non-oxidizing gas atmosphere containing no SiCl ₄ . That is, immediately after the CVD treatment, the Si concentration near the surface of the steel strip is much higher than that in the central portion, and the steel strip is soaked that the Si that is in a rich state on the surface is diffused inside the steel strip. . However, in the present invention, the diffusion heat treatment does not uniformly diffuse Si into the steel strip, and the diffusion treatment is performed while the surface layer Si concentration is higher than the Si concentration in the central portion in the thickness direction of the steel strip. Is cut to form a steel strip having a non-uniform Si concentration in the thickness direction.

From the viewpoint of shortening the diffusion treatment time, the present inventors have examined the relationship between the Si concentration distribution and the magnetic characteristics of the CVD-treated steel material, and as a result, the magnetic characteristics of the high silicon steel material are found to be the grain size of the steel surface layer. It was found that sufficient magnetic characteristics can be obtained without adjusting the Si concentration in the plate thickness direction by adjusting the surface layer portion to a predetermined grain size and Si concentration, which is largely controlled by the Si concentration. It was also found that such a tendency is remarkable especially in high frequency magnetic characteristics.

Therefore, in the present invention, the diffusion process following the CVD process is terminated while the surface layer Si concentration is higher than the Si concentration in the central portion of the steel strip in the thickness direction, and a steel strip having a non-uniform Si concentration in the thickness direction is obtained. It was done like this.

According to such a method, it is possible to obtain a steel strip having sufficiently secured magnetic characteristics by a diffusion heat treatment for a short time. In addition, in the steel strip thus obtained, the central portion of the thickness is maintained at a low Si concentration, so that the toughness is ensured and the fracture of the steel strip can be appropriately prevented.

FIG. 5 shows changes in the Si concentration distribution in the thickness direction of the steel strip in the method of the present invention, showing a case where a steel strip of 3% Si-added steel is used as a base material and this is subjected to a CVD treatment-diffusion treatment. There is. (A) shows the state immediately after the CVD treatment, and Si equivalent to Fe ₃ Si (Si: 14.5%) is deposited on the surface of the steel strip. In the present invention, such a steel strip is subjected to diffusion heat treatment to the state of (B) to obtain a steel strip having a non-uniform Si concentration in the plate thickness direction.
In the example shown in (B), the diffusion heat treatment is performed until the Si concentration of the surface layer reaches 6.5%, and the central portion of the plate thickness is maintained at 3% which is the base material Si concentration.

In the steel strip thus obtained, excellent magnetic characteristics, especially high-frequency magnetic characteristics can be secured by selecting the diffusion heat treatment temperature and the treatment time and adjusting the surface layer portion to an appropriate grain size and Si concentration. .

This diffusion treatment needs to be performed in a non-oxidizing atmosphere so as not to oxidize the surface of the steel strip, and the treatment time is shorter as the temperature is higher.

The diffusion treatment may be carried out at a constant temperature, but Fe in FIG.
As can be seen from the -Si phase diagram, as the diffusion progresses, the Si concentration in the steel strip surface layer decreases and the melting point increases,
The treatment can be performed in a short time by gradually raising the temperature so that the steel strip is not melted with the progress of diffusion (for example, raising the temperature in multiple stages). After such diffusion treatment, the steel strip (S) is cooled in the cooling furnace (4) and then wound up.
Plastic working by rolling is performed in a warm state of 600 ° C. Third
Therefore, the figure shows a concrete example of the structure of the cooling furnace.An intermediate chamber (8) is provided in the middle of the cooling furnace (4).
A skin pass mill (9) is provided in (8). Diffusion furnace (3)
The steel strip (S) exiting from is cooled to a warm state in the front cooling chamber (41) of the cooling furnace (4), then rolled in the skin pass mill (9) of the intermediate chamber (8) and finally cooled. Without being warmed up, it is wound up as it is, or is subsequently cooled to room temperature in the rear cooling chamber (42) and then wound up.

As described above, in the CVD process, Fe on the surface of the steel strip is diffused in the form of FeCl ₂ due to the vapor deposition reaction, and the plate thickness is reduced accordingly. However, the atmospheric gas concentration distribution in the CVD process furnace (2) Due to the non-uniformity, Si vapor deposition is likely to be non-uniform, and therefore the steel strip (S) after the CVD treatment-diffusion treatment has variations in the plate thickness in the width direction and the longitudinal direction. Therefore, in the present invention, 2
By rolling (skin pass rolling or normal rolling) a steel strip (S) in a warm state of 00 to 600 ° C, the plate thickness is made uniform. By such rolling, shape correction and surface roughness adjustment Can be done together. Note that the rolling may be performed with a larger amount of reduction (normal rolling) for the purpose of reducing the plate thickness, instead of light reduction such as skin pass rolling. The present invention is intended to manufacture a high silicon steel strip, and for this reason, the plastic working by rolling is performed in a warm state where the temperature of the steel strip (S) is 200 to 600 ° C. That is, the steel strip temperature is 200
If it is less than ° C, the desired plastic workability cannot be obtained.

The steel strip (S) is usually wound in a warm state from room temperature to 300 ° C. Generally, the Si content is high (for example, 4.0%
Above), it is preferable that the steel strip having a relatively large plate thickness be wound up warm. Therefore, the steel strip (S) is cooled from the hot state to the cooling furnace.
After being cooled to the above temperature range in (4), it is plastically worked by rolling and wound in the warm state as it is, or when it is wound at room temperature, after plastic working by the above rolling, in the latter stage of the cooling furnace. It is finally cooled to room temperature and then wound up.

In the actual line, a plate thickness meter and a profile meter are provided upstream of the mill, and the mill is controlled based on the detection of the plate thickness and plate shape.

Further, in the present invention, after the plastic treatment by the diffusion treatment-cooling and rolling, the steel strip may be continuously coated with an insulating film, and may be wound after the baking treatment. FIG. 2 shows a continuous processing line for this purpose. (6) is a coating device and (7) is a baking furnace.

Electromagnetic steel sheets are usually used in a laminated state, and in this case, each laminated steel sheet needs to be insulated. For this reason, the insulating coating is applied to the electromagnetic steel sheet.

A steel strip having a Si content of 4.0% or more is a brittle material at room temperature and hardly plastically deforms. Therefore, when the insulating film coating is performed on a line different from the CVD processing line, the steel strip may be broken at the time of rewinding and winding of the coil. Therefore, in the present invention, after the plastic processing by diffusion treatment-cooling and rolling, the steel strip (S) is coated with the insulating coating material by the coating device (6) and then baked by the coating baking furnace (7).

As the insulating coating material, an appropriate inorganic or organic coating material can be used. As the inorganic paint, for example, magnesium phosphate, chromic anhydride, silica sol and the like are used, and as the organic paint, plastic resin and the like are used. The paint is applied to the steel strip (S) by a roll coater method, a spray method or the like, and is baked at about 800 ° C. for the inorganic paint and about 200 to 300 ° C. for the organic paint.

In the heating furnace (1), non-oxidative heating is performed.Therefore, heating methods such as electric indirect heating, induction heating, radiant tube indirect heating, and direct heating reduction heating may be used alone or in an appropriate combination. To be taken. When the indirect heating method is adopted, pretreatment such as electric cleaning is performed before heating. As a heating method including pretreatment, for example, the following one can be adopted.

Pretreatment- [Preheating] -Electrical indirect heating (or induction heating) Pretreatment- [Preheating] -Radiant tube heating-Electrical indirect heating (or induction heating) [Preheating] -Open flame reduction heating-Electrical indirect heating (or induction heating) ) Pretreatment- [Preheating] -Radiant tube indirect heating (ceramics radiant tube method) [Preheating] -Direct flame reduction heating There is no particular limitation on the cooling method in the cooling furnace (4), gas jet cooling, mist cooling, radiant cooling. Various cooling methods such as the above can be used alone or in combination.

As described above, the present invention is suitable for the production of steel strips having a very high silicon content such as 6.5% Si steel strip, but conventionally there are many deformations when produced by the rolling method. There is an advantage that a high silicon steel strip having a poor yield of Si: about 2 to 4% can be easily manufactured.

[Example] Example-1 Using a small-sized CVD processing furnace, SiCl for CVD processability
The effects of ₄ concentration and CVD processing temperature were investigated. The results are shown in FIGS. 8 and 9.

In the figure, A is the atmosphere method, that is, the CVD process is performed without nozzle spraying, and B is the nozzle spraying method, that is, the atmosphere gas is sprayed onto the steel strip surface at a flow rate of 0.5 m / s as shown in FIG. A case where the CVD process is performed while being shown. Note that Si
The enrichment ratio is the S of the CVD process for Si at the beginning of the base material.
The i increment is shown.

According to this, the SiCl ₄ concentration is 5% or more, the CVD processing temperature is 1
A large Si enrichment effect is obtained at 023 ° C or higher. Even under the same conditions, the method of spraying the atmospheric gas with the spray nozzle can obtain a significantly superior Si enrichment effect (CVD processability) as compared with the case of simply passing the steel strip in the atmosphere. I understand.

FIG. 10 shows the relationship between the vapor deposition time and the Si concentration in the steel strip (base material Si content + vapor deposition Si content) in the atmosphere method A and the nozzle spraying method B using the same CVD processing furnace. CVD of 0.5 mm thick steel strip with SiCl ₄ concentration of 21% and processing temperature of 1150 ° C
This is an examination of the case of processing. In the nozzle spraying method, atmospheric gas was sprayed from the slit nozzle at a flow rate of 0.2 Nm / sec from the vertical direction to the steel strip. As can be seen from the figure, in order to obtain the Si deposition amount equivalent to 6.5% Si steel, the atmosphere method A takes 7 minutes, whereas the nozzle spray method B
I was able to process it in 1.5 minutes.

FIG. 11 shows the relationship between the collision gas flow rate in the nozzle spraying method and the Si enrichment ratio of the steel strip (similar to FIGS. 8 and 9), which is proportional to the collision gas flow rate up to a predetermined level. The Si enrichment ratio of the steel strip is increasing.

Example-2 By the continuous process shown in FIG.
Steel strips having different diffusion treatment times depending on the amount of vapor deposition were manufactured, and the degree of Si diffusion and magnetic properties of these steel strips were investigated.

Specifically, the plate thickness is 0.35 mm, the plate width is 900 mm, and Si 3%
Change the passage time of the diffusion furnace by changing the line speed in the range of 5 to 50 mpm using the contained steel strip as the material,
A CVD process was performed. In order to prevent the Si deposition amount from changing due to the difference in line speed, change the SiCl ₄ concentration in the CVD atmosphere gas and the atmosphere gas spray amount from the gas spray nozzle according to the line speed. Was adjusted to be constant regardless of the line speed. In this embodiment, the average Si concentration including the base material is 6.5 wt.
Si was vapor-deposited at an amount of vapor deposition so that the concentration became 100%, and a series of treatments was performed by the thermal cycle shown in FIG. For steel strips with a short diffusion treatment time, since the amount of Si in the surface layer is very large, warm steel (25
It was wound at 0-300 ° C.

Fig. 13 shows the steel strip as it is CVD processed, and the diffusion time is 5 each
Min., 10 min., 20 min., 40 min., The Si concentration and the Fe temperature in the cross section in the plate thickness direction were measured by XMA. It has been diffused.

FIG. 14 shows the results of measuring iron loss, which is a magnetic property, of samples obtained by changing the diffusion time under the same conditions as described above. The diffusion treatment time is about 10 minutes, that is, about the time of FIG. 13 (c). It can be seen that sufficiently high magnetic characteristics are obtained, which is almost equivalent to the case where Si is uniformly diffused in the Si diffused state.

For similar material steel strip as in Example -3 Example -2 was CVD process in an atmosphere of various SiCl ₄ concentration by a continuous process, subsequently subjected to a diffusion soaking of 1200 ° C. × 10 minutes, examined the residual degree of voids It was The results are shown in Table 1.

In this way, residual voids were observed at SiCl ₄ concentrations of 30% and 35%. Therefore, for SiCl ₄ concentrations of 30% and 35%, the treatment temperature is A) 1200 ° C. constant × 10 minutes B) 1200 ° C. × 5 minutes → 1250 ° C. × 5 minutes C) 1200 ° C. × 3 minutes → 1250 ° C. × 3 minutes → Steel strips were manufactured at three levels of 1280 ° C x 4 minutes, and the remaining voids were investigated. The results are shown in Table 2.

By selecting the diffusion treatment conditions in this way, SiCl ₄
Even with 35%, a product that is satisfactory to some extent can be obtained. However,
In practice, it is preferable that the concentration of SiCl _{4 is} 30% or less so that the voids can be eliminated by slightly controlling the temperature.

Example-4 In a process line in which the skin pass mill shown in FIG. 3 was incorporated into the continuous process shown in FIG. 1, a steel strip containing 0.33 mm of Si3.5% was used as a base material, and a target was obtained at a line speed of 50 mpm. Si with a plate thickness of 0.30 mm and a width of 900 mm
A steel strip containing 6.5% was produced. At this time, steel strips were manufactured under the following four conditions. In addition, in all cases, the diffusion treatment was performed at 1200 ° C. for 10 minutes.

A) The CVD process is performed in an atmosphere of Ar 80% and SiCl ₄ 20%, and skin pass rolling is not performed.

B) The same CVD process as in A) was performed and skin pass rolling was performed.

C) The CVD process is performed by causing a reaction gas of 80% Ar and 20% SiCl ₄ to collide with the steel strip by a nozzle spraying method at a gas flow rate of 0.5 Nm / s, and does not perform skin pass rolling.

D) CVD treatment is performed in the same manner as C), and skin pass rolling is performed.

Table 3 shows the results of measuring the plate thickness deviation (increase / decrease with respect to the target plate thickness) and the surface roughness of the samples in each of these cases. By performing skin pass rolling, the plate thickness is uniform with high accuracy. You can see that it has changed.

[Effect of the Invention] According to the present invention described above, a high silicon steel strip having excellent magnetic characteristics can be obtained by a short-time swirl CVD treatment and a diffusion heat treatment in a continuous line, and the CVD treatment is performed at a temperature of 1200 ° C. or less. Since it does not cause problems such as defective shape of the steel strip and melting of the edge portion, in addition, excellent toughness can be secured and the plate thickness can be made uniform without impairing the magnetic properties of the steel strip. Therefore, it is possible to efficiently manufacture a high-quality high-silicon steel sheet without increasing the length of the line.

[Brief description of drawings]

1 and 2 are explanatory views showing continuous processing lines for carrying out the method of the present invention. FIG. 3 is an explanatory view showing a specific structural example of the cooling furnace in FIGS. 1 and 2. FIG. 4 is a phase diagram of Fe-Si system. Fig. 5 (A), (B)
Shows changes in the Si concentration distribution in the thickness direction of the steel strip in the diffusion heat treatment of the present invention. Figures 6 and 7 (a), (b)
Shows the state of CVD processing by the nozzle spray method.
FIG. 6 is an overall explanatory view, and FIGS. 7A and 7B are explanatory views showing a nozzle spraying method. Fig. 8 shows the relationship between the SiCl ₄ concentration in the gas and the Si enrichment ratio in the steel strip in the CVD process,
FIG. 9 shows the relationship between the CVD processing temperature and the steel strip Si enrichment ratio. FIG. 10 shows the relationship between the Si deposition time and the Si concentration in the steel strip in the present invention by comparing the atmosphere method and the nozzle spraying method. FIG. 11 shows the relationship between the collision gas flow velocity of the atmospheric gas with respect to the steel strip and the Si enrichment ratio of the steel strip in the CVD process by the nozzle spraying method. FIG. 12 shows the thermal cycle taken in the example. FIGS. 13 (a) to 13 (e) show the Si concentration distribution of each test material in Examples. FIG. 14 shows the magnetic characteristics of each test material in the examples. In the figure, (1) is a heating furnace, (2) is a CVD processing furnace, (3) is a diffusion processing furnace, (4) is a cooling furnace, (6) is a coating device,
(7) is a baking furnace, (9) is a skin pass mill, and (S) is a steel strip.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Publication No. Sho 42-21181 (JP, B1) Japanese Patent Publication No. 47-25655 (JP, B1) Japanese Patent Publication No. 53-42019 (JP, B2)

Claims (2)

[Claims] 1. A non-oxidizing gas containing SiCl ₄ in a mole fraction of 5 to 35% is sprayed onto a steel strip surface from a spraying nozzle while continuously passing the steel strip in an non-oxidizing gas atmosphere. 102
Silica treatment is continuously performed at a temperature of 3 to 1200 ° C., and then S
In the diffusion treatment for diffusing Si into the steel strip in the non-oxidizing gas atmosphere containing no iCl ₄ , the diffusion treatment is
The steel strip is cut off while the surface Si concentration is higher than the central Si concentration in the thickness direction of the steel strip to obtain a steel strip having a non-uniform Si concentration in the thickness direction. A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at a temperature of up to 600 ° C. 2. A steel strip is continuously passed in an atmosphere of non-oxidizing gas, and non-oxidizing gas containing SiCl ₄ in a mole fraction of 5 to 35% is sprayed onto the surface of the steel strip from a spray nozzle. 102
Silica treatment is continuously performed at a temperature of 3 to 1200 ° C., and then S
In the diffusion treatment for diffusing Si into the steel strip in the non-oxidizing gas atmosphere containing no iCl ₄ , the diffusion treatment is
The steel strip is cut off while the surface Si concentration is higher than the central Si concentration in the thickness direction of the steel strip to obtain a steel strip having a non-uniform Si concentration in the thickness direction. A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at ~ 600 ° C, followed by insulating film coating and baking treatment.