JPH0643607B2 - 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, the iron loss decreases as the Si content increases, and Si: 6.5
%, It is known that the iron strain is 0, and the maximum magnetic permeability also has a peak and exhibits the most excellent magnetic characteristics.

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 up to about 4%, but a Si content higher than that can be produced. In that case, cold workability is difficult because the workability is significantly deteriorated. 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 low silicon steel by melting and rolling it into a thin plate, and then permeates Si from the surface to produce a high silicon steel plate. A high silicon steel plate can be obtained without causing any problems.

[Problems to be solved by the invention]

This silicidation 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 are effectively continuous lines. There is a fundamental problem that is not applicable. In addition, since the treatment temperature is extremely high at about 1230 ° C, the shape of the thin steel sheet after the permeation treatment is extremely poor, and the treatment temperature is too high, and the edges may melt due to overheating. We cannot expect stable threading.

Further, in the siliconizing method, Fe on the surface of the steel sheet is diffused in the form of FeCl ₂ or the like due to the vapor deposition reaction, which reduces the sheet thickness. However, in this type of processing, the vapor deposition (film thickness) is likely to be non-uniform due to non-uniformity of the atmospheric gas concentration distribution, etc. As a result, there are variations in the reduction of the plate thickness, and the plate thickness is There is a problem that it tends to be non-uniform in the direction.

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, the basic features of the present invention are as follows.

(1) While continuously passing a steel strip in an atmosphere of non-oxidizing gas, a non-oxidizing gas containing SiCl ₄ in a mol fraction of 5 to 35% is sprayed from a spray nozzle onto the surface of the steel strip to produce 1023 to 12
Continuously silicidized at a temperature of 00 ° C, then SiCl
Diffusion treatment for diffusing Si substantially uniformly inside the steel strip in a non-oxidizing gas atmosphere not containing ₄ is performed, and the steel strip is cooled in a magnetic field in the subsequent cooling process, and before, after or during the cooling in the magnetic field. In, the steel strip is 200 to 600
A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at ℃.

(2) While continuously passing the steel strip in an atmosphere of non-oxidizing gas, a non-oxidizing gas containing 5 to 35% of SiCl ₄ in a mole fraction is sprayed from a spray nozzle onto the surface of the steel strip to produce 1023 to 1
Siliconized continuously at a temperature of 200 ° C, then SiC
A diffusion treatment for diffusing Si substantially uniformly inside the steel strip is performed in a non-oxidizing gas atmosphere containing no l ₄ , and the steel strip is cooled in a magnetic field in the subsequent cooling process, before or after the cooling in the magnetic field, or On the way, the steel strip is 200-60
A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at 0 ° C., final cooling, followed by insulation film coating and baking treatment.

(3) While continuously passing the steel strip in an atmosphere of non-oxidizing gas, a non-oxidizing gas containing 5 to 35% of SiCl ₄ in a mole fraction is sprayed from a spray nozzle onto the surface of the steel strip to produce 1023 to 12
Continuously silicidized at a temperature of 00 ° C, then SiCl
Diffusion treatment for substantially uniformly diffusing Si into the steel strip in a non-oxidizing gas atmosphere not containing ₄ is performed, and during or after the subsequent cooling process, the steel strip is plastically worked by rolling at 200 to 600 ° C., A method for producing a high-silicon steel strip in a continuous line, which comprises performing insulating film coating and baking treatment after final cooling, followed by cooling in a magnetic field in the subsequent cooling process.

(4) While continuously passing the steel strip in an atmosphere of non-oxidizing gas, a non-oxidizing gas containing SiCl ₄ in a mole fraction of 5 to 35% is sprayed from a spray nozzle onto the surface of the steel strip to produce 1023 to 12
Continuously silicidized at a temperature of 00 ° C, then SiCl
Diffusion treatment for diffusing Si substantially uniformly inside the steel strip in a non-oxidizing gas atmosphere not containing ₄ is performed, and the steel strip is cooled in a magnetic field in the subsequent cooling process, and before, after or during the cooling in the magnetic field. In, the steel strip is 200 to 600
A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at ℃, final cooling, insulating film coating and baking treatment, and cooling in a magnetic field in the subsequent cooling process.

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.

3 to 6.5% Si-Fe alloy C: 0.01% or less, Si: 0 to 4.0%, Mn: 2% or less, and other unavoidable impurities are preferably as low as possible.

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

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

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

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 performing 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 treatment temperature in the heating furnace (1) and then introduced into the CVD treatment furnace (2) to obtain SiC.
Silicidation is performed by the CVD method in an atmosphere of non-oxidizing gas containing l ₄ . The non-oxidizing gas containing SiCl ₄ means a neutral or reducing gas, and as the carrier gas of SiCl ₄ , Ar, N ₂ , He, H ₂ , CH _4, etc. can be used.
Of these carrier gases, when considering the processability of exhaust gas, H ₂ , CH _4, etc. generate HCl, and there is a drawback that the process is required, and Ar, He,
N ₂ is preferable, and from the viewpoint of preventing nitriding of the material, Ar and He are particularly preferable among them.

The main reaction of the steel strip surface in the CVD treatment is 5Fe + SiCl ₄ → Fe ₃ Si + 2FeCl ₂ ↑. One Si atom is vapor-deposited on the surface of the steel strip to form a Fe ₃ Si layer, and Fe ₂ atom becomes FeCl ₂ , which is emitted from the steel strip surface in a gaseous state at a temperature of 1023 ° C. or higher of the boiling point of FeCl ₂ . Therefore, since the Si atomic weight is 28.086 and the Fe atomic weight is 55.847, the mass of the steel strip is reduced, and the sheet thickness is also reduced accordingly. By the way, using Si3% steel strip as base material, CVD
If the process produces Si 6.5% steel strip, the mass is reduced by 8.7% and the strip 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 atmospheric gas.

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, in the atmosphere gas in the CVD process,
It specifies the Si concentration and the processing temperature.

First, SiCl in a non-oxidizing gas atmosphere in the CVD process
₄ Concentration is regulated to 5 to 35% by mol fraction, and the steel strip is continuously subjected to CVD treatment in such an atmosphere.

The effect of Si enrichment, which is 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, 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. In other words, the SiCl ₄ concentration is 35%
If it exceeds, voids are remarkably generated and the voids remain even after the diffusion treatment. FIG. 12 shows a cross section of the steel strip immediately after the CVD treatment in the atmosphere of 20% of SiCl _{4, in} which the vapor deposition layer has voids. Figure 13 shows this steel strip at 1200 ℃ ×
It shows the cross section after the diffusion process for 20 min.
The void immediately after the D treatment disappeared almost completely. On the other hand, FIG. 14 shows a cross section of a steel strip which was subjected to a CVD treatment with 40% of SiCl ₄ and then subjected to a diffusion treatment, and it can be seen that voids remain in a layered form.

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 1023.
The temperature is ℃, 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 the basic experiments conducted by the present inventors show that, with the boiling point of FeCl ₂ as a boundary, the enrichment ratio of Si per unit time is remarkably different, and since the vapor deposition rate is lower than 1023 ° C., it is not applicable to a continuous process. Have difficulty. Therefore, the lower limit of 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.
Even when treated at 1230 ° C, which is lower than 50 ° C, the surface of the steel strip partially melts, and the edge of the steel strip melts due to overheating. In this way, the steel strip melts even at temperatures below 1250 ° C because the Si concentration corresponding to Fe ₃ Si is 14.5% or higher on the surface of the steel strip.
Is presumed to have been deposited. On the other hand, if the treatment temperature is 1200 ° C or less, melting of the steel strip surface is not observed at all, and overheating of the edges can be done to about 1220 ° C by setting the average temperature of the steel strip center to 1200 ° C. It has been confirmed experimentally that it can be suppressed and only a small amount of dissolution is required. For the above reasons, the CVD processing temperature is 1023 ° C to 1200
Specified as ° 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. In addition to this, supply and diffusion of SiCl ₄ to the surface of the steel strip and diffusion (desorption) of FeCl _{2 as} a reaction by-product from the surface of the steel strip are required. It is necessary to further increase the CVD processing speed by promoting it.

Conventionally, when the reaction gas is made to flow largely in the VCD process, voids are generated in the vapor deposition layer, and the purity of the vapor deposition layer is also lowered. Therefore, the idea that the gas flow is kept to a necessary minimum has been 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 atmospheric gas containing the reaction gas to the surface of the steel strip one after another, and quickly desorbing the reaction product gas (FeCl ₂ or the like) 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 supply of the reaction gas to the reaction interface and the separation of the reaction product gas from the reaction interface can be promoted.

FIG. 5 shows an implementation situation by this nozzle spraying method. A spray nozzle 5 is arranged in the CVD processing 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. 6 (a) and 6 (b) show the spraying condition by the spraying nozzle, as shown in FIG. 6 (a), from the direction perpendicular to the steel strip surface, or obliquely 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 is obtained at a flow velocity of 5 Nm / sec or less.

The steel strip S subjected to the CVD process as described above is continuously introduced into the diffusion furnace (3) and subjected to the diffusion process in the non-oxidizing gas atmosphere containing no SiCl ₄ . That is, immediately after the CVD treatment, the Si concentration is high near the surface of the steel strip and the base metal S
The i concentration remains as it is, and it is necessary to carry out soaking / diffusion treatment to obtain a uniform 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.

This diffusion process may be performed at a constant temperature, but in FIG.
As can be seen from the Fe-Si phase diagram, as the diffusion proceeds, the Si concentration in the surface layer of the steel strip decreases and its melting point rises.
The diffusion can be promoted by gradually raising the temperature so as not to melt the steel strip (for example, raising the temperature in a plurality of stages) as the diffusion progresses. For example, in the case of 6.5% Si steel, it is possible to raise the temperature to 1400 ° C even if the overheating of the edge portion is taken into consideration.

After such a diffusion treatment, the steel strip S is cooled in a cooling furnace (4) and then wound up. In the present invention, the steel strip is cooled in a magnetic field in this cooling process, and before or in the magnetic field. After medium cooling or in the middle of magnetic field cooling, the steel strip (S) is plastically worked by rolling in a warm state of 200 to 600 ° C.

It is known that the magnetic properties of a silicon steel sheet are significantly improved by cooling it in a magnetic field. In the present invention, the steel strip (S) is passed through a magnetic field in a part of the cooling process to cool the magnetic field. carry out.

The steel strip (S) is affected by magnetism at a temperature below the Curie point, and cooling in a magnetic field exerts a substantial effect at a temperature below the Curie point. In particular, if the steel strip temperature is
The magnetic properties are remarkably improved by performing the process when passing through the A ₂ transformation point. FIG. 15 shows the relationship between the plate temperature of a silicon steel plate and the cooling effect in a magnetic field. For example, in the case of a 6.5 wt% Si steel strip, the temperature t ₁ is the Curie point and the temperature t ₂ is the A ₂ transformation point.
Cooling in a magnetic field requires a temperature T _S higher than the normal temperature t ₁ (eg 750
℃), passes through temperature t ₂ and ends at temperature T _F.

FIG. 16 to FIG. 18 show an example of the configuration of a cooling facility in a magnetic field, and a magnetic field applying coil (8) provided in a cooling furnace.
Is composed of a hollow copper tube (9), and a cooling medium (10) is passed through the copper tube (9) to apply a magnetic field to the steel strip (S) that is passed through the magnetic field applying coil (8). Radiation cooling is performed from the inside surface of the coil while applying the voltage. An insulating film (11) (SiO ₂ or the like) is formed on the outer surface of the copper tube (9).

Water may be used as the cooling medium, but if there is an electrical problem, for example, a fluorine-based inert liquid having a large insulating property may be used.

FIG. 19 shows another configuration example, in which a magnetic field applying coil is used.
A nozzle 12 for supplying cooling gas into the coil is provided at the steel strip exit side position of (8), and further a magnetic field applying coil (8)
The cooling gas introduction duct (15) and the hood (1
4) is provided and the cooling gas is supplied to the outside of the coil by the fan (13).

FIG. 20 shows the apparatus of the system shown in FIGS. 16 to 18 in which the intervals of the magnetic field applying coils (8) (intervals of copper pipes) are sequentially or stepwise from the entrance side to the exit side of the steel strip (S). By making it dense, the uniform cooling and the improvement of the magnetic field cooling effect are achieved. That is, the denser the coil as the cooling body, the higher the cooling rate of the steel strip. Therefore, by passing the steel strip (S) through such a coil,
As shown in the figure, it is possible to cool the steel strip (S) at a constant rate, which enables uniform cooling in the plate thickness direction, and as a result, the transformation is smoothly transferred, which is excellent. Magnetic properties are obtained. Further, the denser the coil, the stronger the magnetic field can be applied to the steel strip, but as described above, the steel strip is strongly affected by the magnetic field in the low temperature region below the Curie point, especially at the A ₂ transformation point. Therefore, a large cooling effect in a magnetic field can be obtained by making the coil dense on the low temperature side and applying a strong magnetic field at least when passing through the A ₂ transformation.

In some cases, contrary to the above, the magnetic field applying coil
It is also possible to adopt a structure in which the intervals of (8) are made closer on the inlet side of the steel strip (S) and are gradually reduced toward the outlet side. With such a structure, the steel strip can be rapidly cooled, and a large magnetic field cooling effect can be secured by keeping the coil relatively dense at least until the steel strip passes the A ₂ transformation point. it can.

Further, in the present invention, the steel strip (S) is plastically worked by rolling in a warm state of 200 to 600 ° C. before, after, or during such cooling in a magnetic field.

As described above, in the CVD process, the vapor deposition reaction causes
Fe is diffused in the form of FeCl _{2 and} the plate thickness is reduced accordingly, but due to the non-uniform atmosphere gas concentration distribution in the CVD processing furnace (2), Si deposition is likely to be non-uniform. ,
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, the steel strip (S) in the warm state is subjected to rolling (skin pass rolling or normal rolling) to make the plate thickness uniform, and such rolling also corrects the shape and adjusts the surface roughness. It 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 for production of high-silicon steel strips, and therefore rolling is performed in a warm state where the temperature of the steel strip (S) is 200 to 600 ° C. That is, if the steel strip temperature is less than 200 ° C, desired plastic workability cannot be obtained.

This plastic working by rolling may be performed before, after, or during the cooling in the magnetic field. As described above, magnetic field cooling is particularly effective in improving magnetic properties by applying a magnetic field when the strip temperature passes the A ₂ transformation point (about 300 ° C for 6.5% Si steel). Therefore, it is preferable to combine the magnetic field cooling and the plastic working by rolling so that the magnetic field cooling is performed when the steel strip temperature passes at least this A ₂ transformation point in the cooling process. The following may be considered as a combination of both processes.

The steel strip (S) is usually wound in a warm state from room temperature to 300 ° C. Generally, a steel strip having a high Si content (for example, 4.0% or more) and a relatively thick plate is wound in the warm state. In this case, it is preferable to wind the film in a warm state after cooling in a magnetic field and rolling as described above.

FIG. 3 shows a concrete structural example of a cooling furnace for performing plastic working by cooling in a magnetic field and rolling. An intermediate chamber (16) is provided in the middle of the cooling furnace (4). A skin pass mill (17) is provided at (16). A magnetic field applying coil (8) is arranged in the front cooling chamber (41) at the front stage of the intermediate chamber. With such equipment, for example, when performing the above steps, the steel strip (S) exiting the diffusion furnace (3) is a cooling furnace (4).
After being cooled to a predetermined temperature in the front cooling chamber (41), it is cooled in the magnetic field to a warm state by continuously passing through the magnetic field applying coil (8), and then the skin pass of the intermediate chamber (16). It is rolled in a mill (17) and wound in the warm state as it is without final cooling, or it is continuously cooled in the rear cooling chamber.
After being cooled to room temperature in (42), it is 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 coating, and the steel strip 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. Therefore, the electrical steel sheet is coated with an insulating film.

A steel strip having a Si content of 4.0% or more is a brittle material at room temperature and hardly plastically deforms. For this reason, when the insulating film coating is performed on a line different from the CVD processing line, the steel strip may be broken when the coil is unwound or wound. 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 case of performing the above-mentioned insulating film coating-baking treatment, the timing of cooling in a magnetic field becomes a problem. That is, in the baking treatment after coating, the coating film may be baked at a high temperature of 700 ° C. or higher.
Even if the cooling in the magnetic field is performed in the cooling after the CVD process-diffusion process which is the previous process, the effect disappears.

Therefore, in the process involving the insulating film coating-baking process, the cooling in the magnetic field can be performed in the cooling process after the diffusion process or the cooling process after the baking process depending on the coating baking temperature and the like. The reheating temperature at which the effect of cooling in a magnetic field disappears is about 6
It is said to be around 50 ° C, so the baking temperature is 65
When the temperature is 0 ° C. or higher, it is preferable to perform magnetic field cooling in the cooling process after the baking treatment, and when the baking temperature is less than 650 ° C., in the cooling process after the CVD treatment-diffusion treatment.

Generally, when baking an inorganic paint, a steel strip is
Therefore, there is no point in heating in a magnetic field before coating in order to heat up to about 0 ° C. Therefore, it is preferable to cool the magnetic field in the cooling process after the baking treatment. Further, in the case of an organic paint, a baking temperature of about 200 ° C. to 300 ° C. is sufficient, and in this case, cooling in a magnetic field can be carried out in the cooling process after the CVD treatment-diffusion treatment.

In some cases, the magnetic field cooling can be performed both in the CVD process-the cooling process after the diffusion process and in the cooling process after the coating-baking process.

As a combination of cooling in a magnetic field and plastic working by rolling in a continuous process involving such insulating film coating-baking treatment, for example, the following is conceivable.

In order to increase the CVD processing rate to the extent that continuous processing of steel strips is possible, it is necessary to optimize the concentration of SiCl ₄ in the atmospheric gas and the processing temperature as described above. By promoting the diffusion of SiCl ₄ into the steel strip and the emission of FeCl ₂ from the surface of the steel strip, the CVD processing rate can be further increased.

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, resulting in nonuniform deposition film thickness.

As a result of further investigation based on such facts, in the CVD processing furnace, the atmosphere gas is blown to the material to be treated by the blowing nozzle, or the atmosphere is forcedly circulated by the fan or the like to the SiCl ₄ steel strip surface. It has been found that the CVD process can be carried out at a high deposition rate while suppressing the non-uniformity of the deposited film, while promoting the diffusion of FeCl ₂ and the diffusion of FeCl _{2 as} a reaction product from the surface of the steel strip.

In order to improve the CVD processability as described above, it is particularly effective to spray atmospheric gas onto the surface of the steel strip with a spray nozzle.
Fig. 5 shows the state of implementation by this nozzle spraying method. The spray nozzle facing the steel strip (S) in the CVD processing furnace (2).
(5) is arranged, and the atmosphere gas containing SiCl ₄ is sprayed on the surface of the steel strip. Figures 6 (a) and (b) show the spraying situation by the spray nozzle (5), which is perpendicular to the steel strip surface as shown in (a) or diagonally as shown in (b). Can be sprayed from any 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.However, 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 rate of 5 Nm / sec or more.

In the heating furnace (1), non-oxidative heating is performed, and therefore, heating methods such as electric indirect heating, induction heating, radiant tube indirect heating, and direct heating reduction heating are used alone or in an appropriate combination. Is 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 an extremely high silicon content such as 6.5% Si steel strip. There is an advantage that a high silicon steel strip having a poor yield of Si: 2 to 4% can be easily manufactured.

EXAMPLES Example -1 small CVD processing furnace - using diffusion treatment furnace, were examined effects of SiCl ₄ concentration and CVD processing temperatures for CVD processing properties. The results are shown in FIGS. 7 and 8.

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 on 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 means the CVD process for the initial Si concentration of the base material.
The increase in Si after the diffusion treatment is shown.

According to this, the SiCl ₄ concentration is 5% or more, the CVD processing temperature is 10%.
A large Si enrichment effect is obtained at 23 ° 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. 9 shows the relationship between the vapor deposition time and the Si concentration in the steel strip (Si concentration after diffusion treatment) in atmosphere method A and nozzle spraying method B using the same CVD treatment furnace-diffusion treatment furnace. , Board thickness 0.5mm
This is a case where the steel strip was subjected to CVD treatment at a SiCl ₄ concentration of 21% and a treatment temperature of 1150 ° C. In the nozzle spray method, the slit nozzle is used to move the steel strip from the vertical direction.
Atmospheric gas was blown at a flow rate of 0.2 Nm / sec. As can be seen from the figure, it is 7 in the atmosphere method A in order to make 6.5% Si steel.
It took about 1.5 minutes, but in the nozzle spray method B, processing could be completed in 1.5 minutes.

Fig. 10 shows the collision gas velocity and steel strip in the nozzle spray method.
It shows the relationship with the Si enrichment ratio (proportion after diffusion treatment). Up to a predetermined level, it is proportional to the collision gas flow velocity
The Si enrichment ratio is increasing.

Example-2 In the continuous process shown in FIG. 1, the plate thickness is 0.35 mm and the plate width is 900 m.
m, Si 3.5% steel strip as base material, line speed 25mpm
Then, a steel strip containing Si: 6.5% was manufactured. In the cooling furnace, cooling is performed in a magnetic field, and in the CVD processing furnace, a SiCl ₄ concentration of 20 mo is used with Ar as a carrier gas by a spray nozzle method.
l% atmosphere gas was blown onto the steel sheet at a gas flow rate of 0.3 Nm / sec. FIG. 11 shows a thermal cycle in this case, and in this example, two-stage heating from 1200 ° C. to 1320 ° C. was performed during the diffusion treatment. As a result, a good quality 6.5% Si steel strip with an extremely low iron loss of W _10/50 : 0.55 W / Kg could be manufactured.

Example 3 A steel strip after the CVD treatment-diffusion treatment was subjected to magnetic field cooling in the cooling process, and its magnetic characteristics were investigated. FIG. 21 shows the results. In the figure, when the magnetic field cooling is not applied, is applied when a magnetic field of 30 Oe is applied by the coil wound with the uniform pitch, as shown in the same figure by the device shown in FIG. In each case, the magnetic field is strengthened in a stepwise manner and the magnetic field is cooled. In particular, the magnetic field cooling is performed by the method of FIG. 20 in which a strong magnetic field is applied before and after passing through the A ₂ transformation point. It can be seen that magnetic characteristics are obtained.

Example-4 In a process line in which the skin pass mill shown in FIG. 3 was incorporated in the continuous process shown in FIG. 1, a Si plate having a thickness of 0.33 mm was used.
Using a 3.5% steel strip as a base metal, a 6.5 mm Si steel strip having a target plate thickness of 0.30 mm and a width of 900 mm was manufactured at a line speed of 25 mpm. At this time, steel strips were manufactured under the following four conditions.

A) The CVD treatment 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 a steel strip at a gas flow rate of 0.3 Nm / S by a nozzle spraying method, 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 1 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 was made uniform with high accuracy. You can see that

[Advantages of the Invention] According to the present invention described above, the CVD process can be carried out in a short time in a continuous line, and the CVD process is carried out at a temperature of 1200 ° C. or less. It is possible to obtain a steel sheet that does not cause a problem, has excellent magnetic characteristics, and has a uniform plate thickness, and as a result, high quality without increasing the length of the line,
It is possible to efficiently manufacture a high silicon steel sheet having high magnetic characteristics.

[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. 5 and 6
FIGS. 5 (a) and 5 (b) show the state of the CVD process by the nozzle spraying method, FIG. 5 is an overall explanatory view, and FIGS. 6 (a) and 6 (b) are explanatory views showing the nozzle spraying method, respectively. . Figure 7 shows C
FIG. 8 shows the relationship between the SiCl ₄ concentration in the gas and the Si enrichment ratio in the steel strip in the VD process, and FIG. 8 shows the relationship between the CVD treatment temperature and the Si enrichment ratio in the steel strip. FIG. 9 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. 10 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. 11 shows the heat cycle in the example of the present invention. 12 to 14 are enlarged microscopic photographs showing the metal structures of the steel strip cross sections of the present invention material and the comparative material, and FIG. 12 is the structure immediately after the CVD treatment in the atmosphere of SiCl ₄ : 20%, The figure shows the microstructure of the steel strip after diffusion heat treatment, and Figure 14 shows the CV at SiCl ₄ : 40%.
It shows the tissue after D treatment and then diffusion treatment.
FIG. 15 shows the relationship between the plate temperature of a silicon steel plate and the cooling effect in a magnetic field. 16 to 18 show an example of the structure of a cooling facility in a magnetic field, and FIG. 16 is a perspective view, FIG.
FIG. 7 is a sectional view of the coil, and FIG. 18 is a sectional view of a copper tube forming the coil. FIG. 19 is an explanatory diagram showing another configuration example of the magnetic field cooling equipment. FIG. 20 is an explanatory view showing a preferable facility for cooling in a magnetic field and a method for cooling in a magnetic field using the facility. FIG. 21 shows the magnetic characteristics in the case of magnetic field cooling in comparison with the case of simple cooling. 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, (8) is a magnetic field applying coil, (9) is a skin pass mill, and (S) is a steel strip.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C23C 16/54 7325-4K (56) References JP-B-45-21181 (JP, B1) JP-B Sho 47-25564 (JP, B1) Japanese Patent Sho 53-42019 (JP, B2)

Claims (4)

[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
Continuous silicidation at a temperature of 3 to 1200 ° C., then
A diffusion treatment for diffusing Si substantially uniformly inside the steel strip is performed in a non-oxidizing gas atmosphere containing no SiCl ₄ , and the steel strip is cooled in a magnetic field in the subsequent cooling process, before or after the cooling in the magnetic field, or On the way, 200 steel strips
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
Continuous silicidation at a temperature of 3 to 1200 ° C., then
A diffusion treatment for diffusing Si substantially uniformly inside the steel strip is performed in a non-oxidizing gas atmosphere containing no SiCl ₄ , and the steel strip is cooled in a magnetic field in the subsequent cooling process, before or after the cooling in the magnetic field, or On the way, 200 steel strips
A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at up to 600 ° C, final cooling, followed by insulation film coating and baking treatment. 3. A steel strip is continuously passed in an atmosphere of non-oxidizing gas, and a non-oxidizing gas containing 5 to 35% of SiCl ₄ in a mole fraction is sprayed onto the surface of the steel strip from a spray nozzle. 102
Continuous silicidation at a temperature of 3 to 1200 ° C., then
Diffusion treatment is performed to diffuse Si substantially uniformly inside the steel strip in a non-oxidizing gas atmosphere containing no SiCl ₄ , and the steel strip is plastically worked by rolling at 200 to 600 ° C. during or after the subsequent cooling process. A method for producing a high-silicon steel strip in a continuous line, which comprises, after final cooling, insulating film coating and baking treatment, followed by cooling in a magnetic field in the subsequent cooling process. 4. A steel strip is continuously passed in an atmosphere of non-oxidizing gas, and a 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
Continuous silicidation at a temperature of 3 to 1200 ° C., then
A diffusion treatment for diffusing Si substantially uniformly inside the steel strip is performed in a non-oxidizing gas atmosphere containing no SiCl ₄ , and the steel strip is cooled in a magnetic field in the subsequent cooling process, before or after the cooling in the magnetic field, or On the way, 200 steel strips
A method for producing a high silicon steel strip in a continuous line, which comprises performing plastic working by rolling at ~ 600 ° C, final cooling, insulating film coating and baking treatment, and cooling in a magnetic field in the subsequent cooling process.