JPH05263247A - Siliconizing treatment of steel sheet for continuous treatment line - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide a method capable of performing siliconizing treatment of a steel sheet in a continuous line without causing problems such as lengthening of the line and non-uniformity of vapor deposition film thickness. [Structure] In a method for siliconizing a steel sheet in a continuous line in which a steel sheet is passed through a chemical vapor deposition treatment chamber and subjected to a siliconizing treatment, in a chemical vapor deposition treatment chamber, an atmospheric gas is perpendicular to a steel plate surface by a spray nozzle. With an inclination angle of 5 to 45
By spraying from an oblique direction of, the supply of the reaction gas to the reaction interface and the separation of the reaction product gas from the reaction interface are significantly promoted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a steel sheet with silicon in a continuous treatment line.

[0002]

2. Description of the Related Art A chemical vapor deposition (hereinafter referred to as CVD) method is known as a method for coating a material to be processed with metal, ceramics or the like. In this CVD method, an atmospheric gas (reaction gas + carrier gas) is supplied to the heated surface of the material to be processed, the reaction gas is brought into contact with the surface of the material to be processed, and the components in the gas are deposited on the surface of the material to be processed by a chemical reaction. It is what makes them. This method has many advantages such as a wide variety of types of coating materials and materials to be treated and excellent coating adhesion and throwing power, and has come to be used in a wide range of fields in recent years. ..

[0003]

Conventionally, there is known a method of obtaining a high-silicon steel sheet by enriching Si in the steel sheet (silicing treatment) by this CVD method. However, this CVD method has a problem that it takes a long time to process due to a low vapor deposition rate of Si, and when it is applied to a steel strip continuous processing line, the processing furnace becomes long, and in addition, the CVD method has a problem. There is a problem that the vapor-deposited film thickness is likely to be non-uniform, and this tendency becomes larger particularly in a continuous line. Therefore, it was practically difficult to apply the CVD method to a continuous production line for high silicon steel sheets. In view of such a problem, the present invention aims to provide a method capable of performing a siliconizing treatment of a steel plate in a continuous line without causing problems such as lengthening of the line and nonuniformity of a vapor deposition film thickness. Is.

[0004]

Means for Solving the Problems The inventors of the present invention have studied the non-uniformity of the vapor deposition rate and the vapor deposition film thickness in the conventional siliconizing treatment of a steel sheet. As a result, they have found that these problems are deeply related to the fluidity of gas at the reaction interface of the steel sheet. That is, conventionally, when a large amount of atmospheric gas is made to flow in a CVD process, vapor deposition unevenness occurs,
It is said that the generation of pores in the vapor-deposited layer or the inclusion of air bubbles in the layer, and further the purity of the vapor-deposited layer is 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, as a result of suppressing the gas flow as described above, conversely, the diffusion transfer of the reaction gas to the steel plate interface and the separation of the reaction by-product (reaction product gas) from the interface surface layer are smooth. It was found that the treatment was not carried out for a long time, and therefore the treatment took a long time, and because the gas flow was suppressed, the concentration of the reaction gas in the treatment chamber was distributed, resulting in a non-uniform deposition film thickness.

As a result of further investigation based on such facts, as a result of spraying an atmospheric gas onto a steel plate surface by a spray nozzle in a CVD processing chamber under a specific condition, a high deposition rate and non-uniform deposition film are formed. It was found that the siliconizing treatment can be performed while suppressing the above.

The present invention has been made on the basis of such findings, and in a method for siliconizing a steel sheet in a continuous line, wherein the steel sheet is passed through a chemical vapor deposition processing chamber to be siliconized, the chemical vapor deposition processing is performed. In the room, the angle of inclination of the atmosphere gas is 5 to 45 with respect to the perpendicular of the steel plate surface by the spray nozzle
Its basic feature is to spray from an oblique direction of °.

By thus performing the gas spraying under a specific condition, it is possible to form a Si vapor deposition film on a steel sheet at a high vapor deposition rate and while suppressing nonuniformity of the vapor deposition film. Generally, the atmospheric gas is sprayed onto the steel sheet at a flow rate of 5 Nm / sec or less. According to such a method of the present invention, for example, by containing SiCl ₄ as a reaction gas in the atmosphere gas and treating the steel sheet with this atmosphere gas, the steel sheet can be enriched with Si uniformly and efficiently. ..

[0008]

The function of the present invention will be described in detail below. In the siliconizing treatment of the steel sheet, a halide such as SiCl ₄ is used as a reaction gas, and Si is deposited on the steel sheet surface by the following reaction. 5Fe + SiCl ₄ → Fe ₃ Si + 2FeCl ₂ ↑

That is, in this reaction, Fe is replaced with Si in the reaction gas on the surface of the steel sheet, 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 steel plate surface, that is, the solid side. Most of what is generally called a CVD reaction is that which is generated (deposited) by the reaction of gas in the gas phase and adheres to the substrate surface.
In the case of this reaction, a by-product (reaction product gas) is generated in the gas phase and is not generated from the solid side. in this way,
In a process involving a substitutional CVD reaction, such as a silicon dioxide treatment of a steel sheet, the reaction product gas exhibits a behavior different from the generally known CVD reaction in that the reaction product gas is generated from the solid side.

In such a substitutional CVD reaction, it is necessary to supply an atmosphere gas containing a reaction gas to the surface of the steel sheet one after another and to quickly release the reaction product gas (FeCl ₂ etc.) from the reaction interface. It is extremely important for promotion. In this sense, spraying the atmosphere gas onto the steel plate surface with a spray nozzle has an 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.

However, also when the atmospheric gas is blown onto the steel sheet surface by the blowing nozzle, there is a large difference in the above-mentioned action and effect depending on the blowing method. 6 (a) and 6 (b) are the case where the atmospheric gas is sprayed from the spray nozzle 3 perpendicularly to the steel plate surface (FIG. 6 (a)) and the case where it is sprayed obliquely (FIG. 6 (b)). 3) schematically shows the gas flow in FIG.

According to this, as shown in FIG. 6 (a), gas (reaction gas: SiC
l ₄ ) is sprayed, a stagnation portion of the atmospheric gas jet is formed on the steel plate surface immediately below the nozzle, and the atmospheric gas successively supplied from the upstream side thereof is a reaction product gas (FeCl ₂ ) Is suppressed, there is no escape area for the reaction product gas, and the gas cannot be separated from the reaction interface. Therefore, the reaction in that part does not proceed. For this reason, the amount of Si enrichment immediately below the nozzle is extremely insufficient as compared with the peripheral portion, a large Si concentration gradient is generated in that portion, and particularly, a portion where the concentration gradient is steep is contracted and deformed. Occurs.

FIG. 7 shows the amount of Si enrichment on the steel plate surface when the atmosphere gas is sprayed from the spray nozzle 3 perpendicularly to the steel plate surface as shown in FIG.
On a 3% silicon steel plate with a thickness of 0.3 mm heated to 50 ° C,
A slit nozzle having a slit size of 10 mm × 400 mm is used to perform a process of blowing an atmosphere gas of SiCl ₄ concentration of 15% and the balance of N ₂ (nozzle-plate distance: 40 mm).
The amount of Si enrichment on the steel plate surface immediately below the nozzle and in the vicinity thereof was examined for each of the treatment times of 0.5 minutes, 1.0 minutes, and 3.0 minutes.

According to FIG. 7, since the separation of the reaction product gas just below the nozzle is hindered as described above, the Si enrichment amount in that portion is extremely insufficient, and a concave Si enrichment distribution is obtained. Therefore, it can be seen that sufficient processing speed is not obtained. Further, when such an extreme Si concentration distribution is generated,
This causes a problem that the portion where the concentration gradient is particularly steep is contracted and deformed. For example, when Si is enriched in a 3% Si steel sheet and Si is increased to 6.5%, the lattice constant (interstitial distance) shrinks by about 0.3%, and as shown in FIG. When a large concentration gradient is generated (when the steepness of the concentration distribution is high), the reaction part of the steel sheet is narrowed and wavy deformation occurs in the plate.

On the other hand, when the atmospheric gas is blown from the oblique direction with an appropriate inclination angle to the steel plate surface as shown in FIG. 6B, the gas stagnation as shown in FIG. As a result, the reaction product gas can be desorbed from the surface of the steel sheet very smoothly, and thus the reaction is greatly promoted and a large processing speed can be obtained. Further, in this method, a fresh reaction gas having a constant concentration is always supplied to the reaction surface, and the reaction product gas is smoothly desorbed from the reaction interface. Does not occur, and in particular, the above-mentioned large Si concentration gradient does not occur in the vicinity immediately below the nozzle, so that the problem of shrinkage deformation due to a rapid Si concentration distribution does not occur.

Here, in order to obtain the above-mentioned effects, the inclination angle θ in the gas spraying direction shown in FIG. 9 is an important factor, and in the present invention, the inclination angle θ with respect to the vertical line of the steel plate surface: The requirement is to blow the atmospheric gas onto the steel plate surface from an oblique direction of 5 to 45 °. FIG. 8 shows the Si enrichment amount of the steel plate surface when the atmosphere gas is blown obliquely to the steel plate surface as shown in FIG. 6 (b). Same as (however, processing time: 3
Minutes). The numerical values in the figure indicate the inclination angle θ in the gas spraying direction with respect to the vertical line of the steel plate surface. As can be seen by comparing with FIG. 7, by providing an appropriate inclination angle in the gas spraying direction, the reaction product gas can be desorbed extremely smoothly, and the reaction can be performed smoothly without the extreme Si concentration distribution shown in FIG. 7. It can be seen that a large processing speed is obtained.
In addition, since a rapid Si concentration gradient is not generated, there is no fear of contraction deformation as described above.

According to FIG. 8, the steepness of the Si concentration distribution changes as the tilt angle θ increases. When the inclination angle θ is about 2.5 °, the Si concentration distribution is steep, and the effect of providing the inclination angle in the gas spraying direction is not sufficiently obtained. On the other hand, when the inclination angle θ is 5 ° or more, the steepness of the Si concentration distribution is small, and a stable concentration distribution is obtained. On the other hand, if the tilt angle θ is large, the Si concentration distribution becomes more uniform, but since the gas flow velocity decreases and the amount of gas colliding with the steel plate decreases, the amount of Si enrichment decreases, and therefore, from the relationship with the processing speed. There is a limit to the size of the tilt angle θ. According to the experiments conducted by the present inventors, it has been found that the treatment can be carried out without causing the problem of the reduction of the Si enrichment when the inclination angle θ is 45 ° or less. For the above reason, in the present invention, the inclination angle θ in the gas spraying direction with respect to the vertical line of the steel plate surface is set to 5 to 45 °.

The present invention can be applied not only to the continuous siliconizing treatment of a coiled steel strip but also to the siliconizing treatment of a single product. In this case, these materials are continuously moved by a belt or the like, Silicone treatment is performed on the way.

FIG. 1 schematically shows the state of the siliconizing treatment of a steel strip according to the method of the present invention. 1 is a heating furnace, 2 is a CVD processing furnace (siliconizing furnace), 3 is a CVD processing furnace. The spray nozzles are arranged, and the spray nozzle 3 sprays the atmospheric gas from the oblique direction (tilt angle θ: 5 to 45 °) on the steel plate surface as shown in FIG. Steel strip S is CVD in heating furnace 1
Heated up to or near the treatment temperature, then C
It is continuously introduced into the VD processing furnace 2. In the CVD processing furnace 2, as shown in FIG. 2, an atmosphere gas containing a reaction gas is blown obliquely from both sides of the steel strip by a blowing nozzle 3 to perform a siliconizing treatment.

FIG. 3 shows the atmosphere gas (SiCl ₄ ) when the Si vapor deposition process is performed by the above continuous line.
The relationship between the flow velocity of (+ carrier gas) (flow velocity at the time of steel strip collision) and the Si deposition rate is investigated. The Si vapor deposition rate increment in this case means the vapor deposition rate of the difference when the Si vapor deposition rate when nozzle spraying is not performed is zero. Here, the Si vapor deposition rate indicates how many moles of Si atoms were vapor deposited per unit time (1 min) for 1 g of the base material. As can be seen from the figure, by spraying the atmospheric gas with the nozzle according to the method of the present invention, the Si deposition rate is remarkably increased. As shown in the figure, the Si deposition rate increases in proportion to the increase in the collision flow velocity of the gas with respect to the steel strip surface. Can not be expected to be effective. Generally, a sufficient effect can be obtained at a flow rate of 5 Nm / sec or less.

[0021]

EXAMPLE Si is vapor-deposited on a cold-rolled steel strip of a normal component by a method of the present invention and a comparative method (a method of performing a siliconizing treatment without spraying nozzles) using a small-sized CVD treatment furnace-diffusion treatment furnace. After the CVD treatment, a diffusion heat treatment was performed to manufacture a high silicon steel strip. FIG. 4 shows the relationship between the SiCl ₄ concentration in the atmosphere gas and the Si enrichment ratio in the steel strip, and FIG. 5 shows the relationship between the CVD treatment temperature and the Si enrichment ratio in the steel strip. A is the method of the present invention (gas collision velocity on the steel strip surface is 0.5 m /
S) and B show those by the comparison method. Note that Si
The enrichment ratio is the siliconizing treatment for the initial Si concentration of the base material.
It means the increase after the diffusion heat treatment. As can be seen from these drawings, in the present invention in which the gas is sprayed from the oblique direction by the spray nozzle, the Si enrichment effect (= vapor deposition rate) is far superior to the comparative method in which the steel strip is simply passed through in the atmospheric gas. ) Has been obtained.

[0022]

According to the present invention described above, since gas stagnation does not occur on the steel plate surface, the reaction product gas can be desorbed from the steel plate surface extremely smoothly, and therefore the reaction is greatly accelerated. , A large processing speed can be obtained.
Further, in this method, a fresh reaction gas having a constant concentration is always supplied to the reaction surface, and the reaction product gas is smoothly desorbed from the reaction interface. Does not occur, and in particular, the above-mentioned large Si concentration gradient does not occur in the vicinity immediately below the nozzle, so that the problem of shrinkage deformation due to a rapid Si concentration distribution does not occur. From the above, a silicon steel plate with excellent quality can be efficiently manufactured by a continuous line.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state of spraying atmospheric gas by the spray nozzle of FIG.

FIG. 3 is a graph showing the relationship between the atmospheric gas flow rate and the Si deposition rate in the method of the present invention.

FIG. 4 is a graph showing the relationship between the SiCl ₄ concentration in the atmosphere gas and the Si enrichment ratio in the steel strip for the method of the present invention and the comparative method.

FIG. 5 is a graph showing the relationship between the CVD processing temperature and the enrichment ratio of Si in the steel strip for the method of the present invention and the comparative method.

FIG. 6 is an explanatory view schematically showing the flow of gas when the atmospheric gas is sprayed from the spray nozzle 3 perpendicularly to the steel plate surface and when it is sprayed obliquely.

FIG. 7 is an explanatory diagram showing the amount of Si enrichment on the steel plate surface when the atmospheric gas is sprayed from the spray nozzle perpendicularly to the steel plate surface.

FIG. 8 is an explanatory diagram showing the amount of Si enrichment on the steel plate surface when an atmosphere gas is sprayed obliquely onto the steel plate surface by a spray nozzle.

FIG. 9 is an explanatory diagram that defines a tilt angle θ in a gas spray direction from a spray nozzle.

[Explanation of symbols]

1 ... Heating furnace, 2 ... CVD processing furnace, 3 ... Spray nozzle, S ...
Steel strip

Claims (1)

[Claims] 1. A method for siliconizing a steel sheet in a continuous line, wherein the steel sheet is passed through a chemical vapor deposition treatment chamber to be subjected to a siliconizing treatment. Inclination angle 5 to the perpendicular of
A method for siliconizing a steel sheet in a continuous processing line, which comprises spraying the steel sheet surface from an oblique direction of 45 °.