JPH0643609B2 - Method for producing high silicon steel strip in continuous line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates 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).

[Prior Art] A high silicon steel plate is used as an 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, when%, the magnetostriction becomes 0, and the maximum magnetic permeability also has a peak and exhibits the best 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 becomes difficult because the workability deteriorates significantly. Further, the direct casting method, so-called strip casting, does not cause the problem of workability unlike the rolling method, but it is still a developing technology, and it is easy to cause shape defects, and it is particularly difficult to manufacture a high silicon steel sheet.

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. It is a long time of 30 minutes or more, and the diffusion heat treatment performed after the CVD process requires a relatively long time because the vapor-deposited Si needs to be evenly diffused inside the base material. There's a problem. Also, since the CVD treatment temperature is as high as about 1230 ° C, the shape of the thin steel sheet after the infiltration treatment is extremely poor,
In addition, since the processing temperature is too high, the edge portion may be melted by overheating, and stable threading in a continuous line cannot be expected.

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 the Problem] Therefore, according to the present invention, a non-oxidizing gas containing SiCl ₄ in a mol fraction of 5 to 35% while continuously passing a steel strip in an non-oxidizing gas atmosphere. Is sprayed onto the surface of the steel strip from a spraying nozzle and continuously subjected to silicidation treatment at a temperature of 1023 to 1200 ° C., and then Si in a non-oxidizing gas atmosphere containing no SiCl _4.
In the diffusion treatment for diffusing the inside of the steel strip, the diffusion treatment is terminated while the surface layer Si concentration is higher than the Si concentration in the central portion in the thickness direction of the steel strip, and the Si concentration is uneven in the thickness direction. Its basic feature is to obtain a steel strip, cool it in a magnetic field in a part of the subsequent cooling process, and then wind it.

Further, the present invention, after the diffusion treatment-cooling, an insulating film coating is applied, and after the baking treatment, it is wound,
Another basic feature is that the cooling in the magnetic field is performed in a cooling process after the diffusion process, a cooling process after the baking process, or a part of both cooling processes according to the coating baking temperature and the like.

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, 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%, 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, 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.

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 to form SiCl.
Silicidation is performed by a CVD method in an atmosphere of non-oxidizing gas containing 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 and the} like generate HCl, which makes it necessary to process HCl, and Ar, He, N ₂ which do not cause such a problem. 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 _{process, 5Fe + SiCl 4 → Fe 3} Si + 2FeCl a ₂ ↑. One Si atom is vapor-deposited on the surface of the steel strip to form a Fe ₃ Si layer, Fe ₂ atom becomes FeCl ₂ , and the boiling point of FeCl ₂ is 1023 ℃.
At the above temperatures, it is emitted from the surface of the steel strip in a gaseous state. Therefore, since the Si atomic weight is 28.086 and the Fe atomic weight is 55.847, the mass of the steel strip decreases, and the plate thickness also decreases accordingly. By the way, using Si3% steel strip as the base material,
When Si6.5% steel strip is manufactured by CVD process, the mass is 8.7%.
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 treatment conditions were not sufficiently examined. 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.

Acceleration of diffusion of SiCl _{4 to} the steel strip surface and diffusion 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, SiC in a non-oxidizing gas atmosphere in the CVD process
The l ₄ concentration is specified to be 5 to 35% in terms of mol fraction, and the steel strip is subjected to continuous 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 more than 5 minutes are required 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.

Also, 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 rarely seen up to a SiCl ₄ concentration of around 15%, but begins to form when it exceeds 15%. But,
When the SiCl ₄ concentration is 35% or less, CV is generated even if voids are generated.
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 long-time diffusion soaking treatment. 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 the diffusion process.

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 the 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. 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 about 1230 ° C, which is lower than 50 ° C, the surface of the steel strip is partially melted, and the edge portion of the steel strip is melted due to overheating. In this way, the steel strip melts even at temperatures below 1250 ° C because the surface of the steel strip has a Si concentration equivalent to Fe ₃ Si of 14.5% or higher.
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 edge can be reduced 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, 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 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 spraying 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 guided to 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 near the surface of the steel strip is much higher than that in the central portion, and the surface of the steel strip is over-concentrated by soaking the steel strip.
A process of diffusing Si inside the steel strip is performed. However, in the present invention, the diffusion heat treatment does not uniformly disperse Si in the steel strip, and the diffusion treatment is performed while the surface layer Si concentration is higher than the Si concentration in the steel strip thickness direction central portion. Is cut off to form a steel strip having a non-uniform Si concentration in the thickness direction.

The inventors of the present invention have studied the relationship between the Si concentration distribution and the magnetic characteristics of the CVD-treated steel from the viewpoint of shortening the diffusion processing time. As a result, the magnetic characteristics of the high-silicon steel are found to be the grain size of the steel surface layer. It was found that sufficient magnetic properties can be obtained even if the Si concentration is not uniform 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 treatment subsequent to the CVD treatment is terminated while the surface layer Si concentration is higher than the Si concentration in the central portion in the thickness direction of the steel strip, 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, the steel strip thus obtained has a low
Since the Si concentration is maintained, the toughness is secured and the fracture can be appropriately prevented.

FIG. 4 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 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 (B) state 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.

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

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 it is performed at a higher temperature.

The diffusion treatment may be performed 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 surface layer of the steel strip decreases and its melting point rises. By raising the temperature in step 1), the treatment can be performed in a short time.

After such diffusion treatment, the steel strip S is cooled in the cooling furnace 4,
Then, the steel strip S is wound up in a magnetic field in a part of this cooling process.

It is known that the magnetic properties of a silicon steel sheet are remarkably 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 perform cooling in a magnetic field. .

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, the steel strip temperature is A when cooling in a magnetic field.
_The magnetic properties are remarkably improved by performing the process when passing through the _two transformation points. FIG. 11 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 6.5 wt% Si steel strip,
The temperature t ₁ is the Curie point, the temperature t ₂ is the A ₂ transformation point, the cooling in the magnetic field is started from the temperature T _S higher than the normal temperature t ₁ (for example, 750 ° C.), and passes the temperature t ₂ to reach the temperature. T
End with _F.

FIGS. 12 to 14 show an example of the configuration of a cooling facility in a magnetic field. The magnetic field applying coil 8 provided in the cooling furnace is composed of a hollow copper tube 9, and the cooling medium 10 is placed in the copper tube 9. The steel strip S which is passed through the coil 8 for applying a magnetic field by passing
Radiation cooling is performed from the inside surface of the coil while applying a magnetic field to the coil. An insulating film 11 (such as SiO ₂ ) is formed on the outer surface of the copper tube 9.

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

FIG. 15 shows another configuration example, in which the magnetic field applying coil 8 is used.
Nozzle 12 for supplying cooling gas to the inside of the coil is provided at the steel strip exit side position, and further, cooling gas introduction duct 15 and hood 14 are provided above and below the magnetic field applying coil 8,
The cooling gas is supplied to the outside of the coil by the fan 13.

FIG. 16 shows that in the apparatus of the system shown in FIGS. 12 to 14, the distance between the magnetic field applying coils 8 (the distance between the copper pipes) is the steel strip S.
It is intended to achieve uniform cooling and improvement of the magnetic field cooling effect by sequentially or stepwise increasing the density from the inlet side to the outlet side. That is, the denser the coil as the cooling body, the greater the cooling of the steel strip. Therefore, by passing the steel strip S through such a coil, the steel strip S is cooled at a constant speed as shown in FIG. It is possible to achieve uniform cooling in the plate thickness direction, and as a result, the transformation can be smoothly transferred and excellent magnetic characteristics can be obtained. Further, the denser the coil is, the stronger the magnetic field can be applied to the steel strip. However, as described above, the steel strip is strongly affected by the magnetic field in the low temperature region below the Curie point, particularly 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 point.

In some cases, conversely to the above, a structure may be adopted in which the magnetic field applying coils 8 are closely spaced on the entrance side of the steel strip S and are gradually sparse toward the exit 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.

The steel strip S is cooled as described above and wound on the coil. In this case, it is generally preferable that a steel strip having a high Si content (for example, 4.0% or more) and a relatively thick plate is wound in a warm state.

Further, in the present invention, after the diffusion treatment-cooling, 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, in which 6 is a coating apparatus 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. Steel strips with Si content of 4.0% or more are brittle materials at room temperature,
Almost no plastic deformation. Therefore, when the insulating film coating is performed on a line different from the CVD processing line, the steel strip may be broken during the coil rewinding and winding. Therefore, according to the present invention, after the diffusion treatment and cooling, the steel strip S is coated with an insulating coating material by the coating device 6, and then is baked in the coating baking furnace 7.

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

In the case of performing the insulating film coating-baking process as described above, the timing of cooling in a magnetic field becomes a problem. That is, in the baking process after coating, the coating film may be baked at a high temperature of 700 ° C. or higher, and if such high temperature baking is performed, cooling in a magnetic field is performed in the cooling process after the CVD process-diffusion process which is the previous step. However, the effect disappears.

Therefore, in the step of performing insulating film coating-baking treatment, cooling in a magnetic field can be performed in the cooling process after the diffusion treatment or the cooling process after the baking treatment, 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 650.
It is said to be around ℃, so when the baking temperature is 650 ℃ or higher, it is in the cooling process after baking, and when the baking temperature is less than 650 ℃, it is in the cooling process after CVD treatment-diffusion treatment. It is preferable to perform cooling in each magnetic field.

Generally, when baking an inorganic paint, the steel strip is heated to about 800 ° C. Therefore, cooling in a magnetic field before coating is meaningless in this case, and cooling in a magnetic field is performed in the cooling process after baking. Preferably. Further, in the case of an organic paint, a baking temperature of about 200 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.

The cooling in the magnetic field can be performed in both the cooling process after the CVD process-diffusion process and the cooling process after the coating-baking process, depending on the case.

Oxidation-free heating is performed in the heating furnace 1. Therefore, heating methods such as electric indirect heating, induction heating, radiant tube indirect heating, and direct-fire reduction heating may be used individually or in an appropriate combination. 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 can be adopted: pretreatment- [preheating] -electric indirect heating (or induction heating) pretreatment- [preheating] -radiant tube heating-electric indirect heating (or induction heating) ) [Preheat] -Direct heating / reduction heating-Electrical indirect heating (or induction heating) Pretreatment- [Preheating] -Radiant tube indirect heating (ceramic radiant tube method) [Preheating] -Direct heating / reduction heating The cooling method is not particularly limited, and various cooling methods such as gas jet cooling, mist cooling, and radiation cooling 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. However, there are many deformations when conventionally produced by the rolling method. There is an advantage that a high-silicon steel strip having a low yield of Si: about 2 to 4% can be easily manufactured.

[Example] ○ Example-1 Using a small-sized CVD processing furnace, SiC with respect to CVD processability
l ₄ was investigated the effect of concentration and CVD processing temperatures. 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 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. In addition,
The Si enrichment ratio refers to the amount of increase in the amount of Si after the CVD process with respect to the amount of Si in the initial of the base material.

According to this, the SiCl ₄ concentration is 5% or more, the CVD processing temperature
A large Si enrichment effect is obtained above 1023 ° C.
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 same CVD process furnace using the atmosphere method A and the nozzle spraying method B for the deposition time and the Si concentration in the steel strip (the amount of the base material Si + the deposition).
The relationship with the amount of Si) is as follows: Si: 3%, steel strip 0.5 mm thick
l ₄ concentration of 21% is obtained examined case of CVD at a treatment temperature of 1150 ° C.. In the nozzle spray method, 0.2 Nm /
Atmospheric gas was blown at a flow rate of sec. As can be seen from the figure, the atmosphere method A was used to obtain the Si deposition amount equivalent to 6.5% Si steel.
It took 7 minutes, whereas in the nozzle spraying method B, it could be processed in 1.5 minutes.

Figure 10 shows the collision gas velocity and Si of steel strip in the nozzle spraying method.
It shows the relationship with the enrichment ratio (similar to FIGS. 7 and 8), and the Si enrichment ratio of the steel strip increases in proportion to the collision gas flow velocity up to a predetermined level.

○ Example-2 By the continuous process shown in Fig. 1, steel strips having different diffusion treatment times with the same amount of Si vapor deposition were produced, and the degree of Si diffusion and magnetic properties of these steel strips were investigated.

Specifically, using a steel strip with a plate thickness of 0.35 mm and a plate width of 900 mm and containing 3% Si, the line time is changed within the range of 5 to 50 mpm to change the passage time of the diffusion furnace, and the CV
D treatment (CVD treatment temperature 1050-1150 ° C.)-Diffusion treatment. In addition, in order to prevent the amount of Si vapor deposition from changing due to the difference in line speed, CV should be adjusted according to the line speed.
D The SiCl ₄ concentration in the atmosphere gas (10 to 30%) and the amount of atmosphere gas sprayed from the gas spray nozzle were changed so that the amount of Si deposited was constant regardless of the line speed.
In this example, Si was deposited in such an amount that the average Si concentration including the base material was 6.5 wt%, and the series of treatments was performed in the 18th step.
The thermal cycle shown in the figure was used. For steel strips with a short diffusion treatment time, since the amount of Si in the surface layer is very large, a warm (250 to 300 ° C) temperature was used to prevent cracking of the surface layer.
I wound up with.

Fig. 19 shows the steel strip as it is CVD processed and the diffusion time is 5 each
Min., 10 min., 20 min., 40 min. Of the above steel strip, the Si concentration and the Fe concentration in the cross section in the plate thickness direction were measured by XMA. Has been diffused.

Figure 20 shows the results of measuring the iron loss, which is the magnetic property, for cycles obtained by changing the diffusion time under the same conditions as above, and the diffusion treatment time was about 10 minutes, that is, Figure 19
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 diffusion state of about (C).

○ Example-3 The same material steel strip as in Example-2 was subjected to a CVD process in an atmosphere of various SiCl ₄ concentrations by a continuous process, and subsequently subjected to a diffusion soaking treatment at 1200 ° C for 10 minutes to determine the degree of voids remaining. Examined. The results are shown in Table 1.

Thus, residual voids were observed in SiCl ₄ 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 set at three levels of 1280 ° C x 4 minutes were manufactured, and their residual 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 satisfied to some extent can be obtained. However, in practice, it is preferable that the SiCl ₄ concentration is 30% or less so that the voids can be eliminated by a slight temperature control.

○ Example-4 The steel strip after the CVD treatment-diffusion treatment was cooled in a magnetic field in the cooling process, and its magnetic characteristics were investigated.

FIG. 17 shows the results. In the figure, when the magnetic field cooling is not applied, is the material of the present invention, of which, when a magnetic field of 30 Oe is applied by the coil wound at a uniform pitch, The apparatus shown in FIG. 16 shows the case where the magnetic field is gradually strengthened and cooled in the magnetic field as shown in FIG. Further, 'and' are comparative materials, in which vapor-deposited Si is uniformly diffused in the steel strip, of which, 'is the same as and the same is the same as that in the magnetic field. As is clear from the figure, the magnetic material of the present invention has magnetic characteristics comparable to those of the comparative material in which Si is uniformly diffused. Further, it is found that particularly excellent magnetic characteristics are obtained by carrying out cooling in a magnetic field by the method of FIG. 16 in which a strong magnetic field is applied before and after passing through the A ₂ transformation point.

[Effects of the Invention] According to the present invention described above, a high silicon steel strip having excellent magnetic properties can be obtained by a short-time CVD treatment and a diffusion heat treatment in a continuous line, and C at a temperature of 1200 ° C or lower.
Since the VD process is performed, problems such as defective shape of the steel strip and melting of the edge portion do not occur, and in addition, the toughness of the steel strip can be improved without impairing the magnetic properties. It is possible to efficiently manufacture a high-quality silicon steel sheet having high quality and high magnetic properties without increasing the length of the steel sheet.

[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 Fe-Si system phase diagram. FIGS. 4 (A) and 4 (B) show changes in the Si concentration distribution in the thickness direction of the steel strip during the diffusion heat treatment of the present invention. FIGS. 5 and 6 (a) and (b) show the state of the CVD process by the nozzle spraying method. FIG. 5 is an overall explanatory diagram,
6 (a) and 6 (b) are explanatory views showing the nozzle spraying method. Figure 7 shows SiCl ₄ in gas during CVD processing.
FIG. 8 shows the relationship between the concentration and the Si enrichment ratio in the steel strip, 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 relationship between the plate temperature of a silicon steel plate and the cooling effect in a magnetic field. 12 to 14 show an example of the configuration of a cooling facility in a magnetic field, FIG. 12 is a perspective view, FIG. 13 is a sectional view of a coil, and FIG. 14 is a sectional view of a copper tube constituting the coil. Is. First
FIG. 15 is an explanatory diagram showing another configuration example of the magnetic field cooling equipment. FIG. 16 is an explanatory view showing a preferable facility for cooling in a magnetic field and a method for cooling in a magnetic field by the facility. FIG. 17 shows the magnetic characteristics in the case of magnetic field cooling in comparison with the case of simple cooling. FIG. 18 shows the thermal cycle taken in the example. FIGS. 19 (a) to 19 (e) show the Si concentration distribution of each test material in Examples. FIG. 20 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 apparatus, 7 is a baking furnace, 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 (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
Continuous silicidation at a temperature of 3 to 1200 ° C., then
In the diffusion treatment for diffusing Si into the steel strip in the non-oxidizing gas atmosphere containing no SiCl ₄ , the diffusion treatment is performed such that the surface Si concentration is higher than the Si concentration in the central portion in the thickness direction of the steel strip. A method for producing a high-silicon steel strip in a continuous line, which is characterized in that the steel strip is cut off in the inside to obtain a steel strip having a non-uniform Si concentration in the thickness direction, and the steel strip is cooled in a magnetic field in a part of the subsequent cooling process and then wound. . 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
In the diffusion treatment for diffusing Si into the steel strip in the non-oxidizing gas atmosphere containing no SiCl ₄ , the diffusion treatment is performed such that the surface Si concentration is higher than the Si concentration in the central portion in the thickness direction of the steel strip. The steel strip is cut out and the Si concentration is non-uniform in the thickness direction. After cooling, an insulating film coating is applied and baking is performed, and then winding is performed after cooling, and the cooling process after the diffusion process and / or the baking process is performed. A method for producing a high-silicon steel strip in a continuous line, which comprises cooling the steel strip in a magnetic field in a part of the cooling process.