JP2528748B2 - Method of manufacturing silicon steel sheet by continuous line - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a silicon steel sheet by a diffusion infiltration method.

[0002]

2. Description of the Related Art Silicon steel sheets are widely used as core materials for transformers and motors because of their excellent soft magnetic properties. It is known that this type of steel sheet exhibits excellent magnetic properties such that the iron loss is reduced as the Si content increases, and the magnetostriction becomes 0 when the Si content is 6.5 wt%, and the maximum magnetic permeability also peaks. Conventionally, there are a rolling method, a direct casting method and a diffusion infiltration method as a method for producing a silicon steel sheet. Among them, the rolling method can produce a Si content up to about 4 wt%, but if the Si content is higher than that, Cold workability becomes difficult because the workability is significantly deteriorated. Further, the direct casting method does not have the problem of workability unlike the rolling method, but has many problems, such as easy occurrence of shape defects, and the inability to produce thick or wide materials.

On the other hand, in the diffusion infiltration method, low silicon steel is melted in advance and thinned by rolling, and then Si is applied from the surface.
A silicon steel sheet is manufactured by infiltrating the steel sheet. According to this method, the silicon steel sheet can be obtained without causing a problem of workability. The production of silicon steel sheets by this diffusion infiltration method is generally performed by using ordinary steel sheets or low silicon steel sheets (usually S
i: 4 wt% or less) is subjected to Si infiltration treatment (siliconization treatment) in an atmosphere of non-oxidizing gas containing Si compound such as SiCl ₄ to infiltrate Si from the surface of the steel sheet, and then Si compound A steel sheet is subjected to a diffusion heat treatment in a non-oxidizing gas atmosphere containing no oxygen to diffuse the permeated silicon into the steel sheet to obtain a silicon steel sheet containing Si uniformly.

Conventionally, with respect to this type of manufacturing method, various conditions for continuously treating a steel sheet have not been sufficiently examined, and the treatment time is as long as 30 minutes or more, and the treatment temperature is 1
There is a problem that the processing conditions cannot be applied to a continuous line practically, such as 230 ° C., which is extremely high and the edge part may be melted, and stable production in a continuous line of steel sheets cannot be expected.

To address such a problem, the present applicant first
A method for producing a silicon steel sheet in which the diffusion and infiltration method is applied to a continuous line is disclosed in JP-A-62-227078 and JP-A-62-2.
Proposed as No. 27091. These methods, heating the steel sheet after continuously siliconizing treatment by chemical vapor deposition in a non-oxidizing gas atmosphere containing SiCl _4, SiCl ₄
Diffusion annealing in a non-oxidizing gas atmosphere containing no Si
It relates to a method for producing a silicon steel sheet efficiently by serializing a series of processes for homogenizing and cooling and coiling it into a coil. Reaction gas concentration, reaction time, soaking at the time of siliconizing in a continuous line. The diffusion processing time and the processing temperature are studied and specified in detail, and it is possible to manufacture a silicon steel sheet by diffusion permeation processing in a continuous line.

[0006]

However, according to the subsequent studies by the present inventors, the manufacturing method in which the processing conditions are specified as described above solves the problem which has hitherto been an obstacle to continuous line formation, Although it is possible in principle to efficiently manufacture a silicon steel sheet, it has been found that there is a new problem that a significant shape defect occurs in the steel sheet due to the siliconizing treatment. Conventionally,
Regarding the shape control of such a product steel sheet, there is no detailed study. The present invention provides a method for manufacturing a silicon steel sheet by such continuous diffusion and permeation treatment of Si,
It is an object of the present invention to provide a method for continuously and stably producing a flat and high-quality silicon steel sheet having no shape defect.

[0007]

The present invention relates to a method for producing a silicon steel sheet by subjecting a steel sheet to a siliconizing treatment for infiltrating Si from its surface in a reaction furnace and diffusing this Si in the sheet thickness direction. , To prevent defective shape of steel plate,
By defining the length of the siliconizing zone (reactor length) according to the amount of siliconizing, the thickness of the steel sheet and the width of the steel sheet, the Si increase gradient (wt% / m) in the longitudinal direction of the steel sheet due to the siliconizing treatment Is to be kept below a predetermined value, and the feature is that a plurality of slit nozzles are arranged at intervals of 1 m or less in the furnace longitudinal direction above and below the plate passing portion in the furnace, and The steel plate is passed through a reaction furnace having a satisfactory furnace length L (m), and the reaction gas is blown from the slit nozzle to the steel plate to perform the siliconizing treatment on the steel plate.

[Equation 2]

Here, the raw steel plate is a normal steel plate or a non-oriented or oriented silicon steel plate having a relatively low silicon content (usually 4 wt% or less). The reaction gas used in the siliconizing treatment of the present invention is a mixed gas of a Si compound such as SiCl ₄ and a non-oxidizing gas (usually an inert gas). To be sprayed.

[0009]

The details of the present invention will be described below. When manufacturing a high silicon steel sheet by adding Si to a low silicon steel sheet by continuous siliconization treatment, it is important that the siliconization reaction can be easily controlled and the amount of Si added can be accurately adjusted. For this purpose, it is most preferable to control the amount of Si by spraying the reaction gas from the nozzle onto the steel sheet and adjusting the parameters such as the flow rate, the concentration and the flow rate. From such a viewpoint, in the present invention, a plurality of slit nozzles 2 are arranged at intervals in the longitudinal direction of the furnace at the upper and lower positions of the steel plate passage portion in the present invention, and the slit nozzles 2 are connected to the steel plate 1 as shown in FIGS. 1 and 2. Basically, the steel sheet is continuously subjected to a siliconizing treatment by spraying a reaction gas.

In the continuous siliconizing treatment as shown in FIG. 3, the Si concentration of the steel sheet continuously increases in the treatment furnace as shown in the figure, and a Si concentration distribution occurs in the longitudinal direction of the steel sheet. Then, since the lattice constant decreases as shown in FIG. 5 due to the increase of Si in the steel sheet, the steel sheet shrinks in the processing furnace. Therefore, a stress acts on the steel plate which is a continuum in the plate width direction, and when the stress value exceeds the critical stress value,
The steel plate undergoes deformation such as plate drawing and edge flipping during the siliconizing process. Therefore, it is very important to alleviate the compressive stress in the plate width direction generated by the contraction of the steel plate due to the continuous siliconizing treatment to the extent that no deformation occurs and prevent the deformation of the steel plate.

The stress in the width direction (particularly the compressive stress) that causes the defective shape of the steel sheet depends on the amount of contraction of the sheet width per unit length of the steel sheet. For this reason, in order to relieve this stress, it is necessary to gradually perform the siliconizing treatment with a sufficient length in the longitudinal direction of the steel sheet. Therefore, the inventors of the present invention, based on a stress theory, a mechanical property test, and a siliconizing treatment test, perform a continuous siliconizing treatment on a steel sheet, and a necessary minimum siliconized area length L ₁ (so as not to cause plate deformation. m) was derived as in equation (1).

(Equation 3)

Here, when the reaction gas is sprayed from the slit nozzle 2 to the steel plate 1 as shown in FIGS. 1 and 2, the reaction amount is the largest just below the nozzle (slit 3) and decreases as the distance from the immediately below the nozzle increases. To do. Therefore,
When the distance between the nozzles is large, there is a possibility that some reaction may not occur between the nozzles. This part cannot be regarded as a siliconized region, and the furnace length and the siliconized region length cannot be considered equal. Therefore, the minimum nozzle arrangement interval was determined by changing the nozzle arrangement interval and measuring the length of the portion where no reaction occurred. The result is shown in FIG. According to this, it has been found that there is a portion where there is no reaction between the nozzle arrays unless the distance between the nozzles is 1 m or less. Therefore, the present invention is premised on the slit nozzles having an interval of 1 m or less. The siliconizing process is also affected by the distance between the nozzle and the steel plate, and it is premised that the gas blown out from the nozzle is not affected by the bulk gas flow (atmosphere gas flow). Was set to be 15 times or less the slit width.

FIG. 7 to FIG. 9 show some examples of the test results for obtaining the above formula (1). The larger the plate width of the raw steel plate and the thinner the plate thickness, the more the siliconized region. It is necessary to take a long length and perform a siliconizing treatment that gradually increases the Si concentration in the longitudinal direction of the steel sheet, and a raw steel sheet having an arbitrary sheet thickness t, sheet width w, and Si amount: S ₁ (wt%). When a steel sheet having an average Si content in the plate thickness direction: S ₂ (wt%) is manufactured by subjecting the steel to continuous siliconization treatment, a minimum siliconization region length L ₁ (m) or more defined by the above formula (1) is required. The length of the siliconized region (reactor length) must be set. In order to verify the above formula (1), the present inventors used the manufacturing line shown in FIG. 3 and conducted a continuous siliconizing treatment test on steel sheets of various sizes. As a result, it has been confirmed that the present formula can be applied to the plate width up to the maximum 1800 mm that can be manufactured at present, and the plate thickness in the range of 0.05 to 1.0 mm.

Therefore, the nozzles are arranged under the above conditions, and the continuous siliconizing process is performed by spraying the reaction gas from the nozzles onto the steel plate with the siliconizing region length (reactor furnace length) longer than the minimum siliconizing region length L _1. Only by rubbing, a silicon steel plate having a good shape can be manufactured.

Regarding the flow rate of the gas blown from the nozzle, if the flow rate is less than 0.5 m / sec, the bulk flow has a large effect, while if it exceeds 3.5 m / sec, the amount of gas supplied to the furnace is enormous. Therefore, in this case also, the gas flow rate is affected, so the gas flow rate is preferably 0.5 to 3.5 m / sec. Further, with respect to the concentration of the reaction gas, if the concentration is less than 5 vol%, the reaction amount is extremely small, and a sufficient siliconizing reaction does not occur. On the other hand, if it exceeds 40 vol%, the reaction amount immediately below the nozzle increases, so that a rapid reaction occurs locally and plate deformation occurs. For this reason, the reaction gas concentration is preferably 5 vol% to 40 vol%.

The siliconizing temperature of the steel sheet is 1050 ° C.
If it is less than 1250 ° C, a sufficient reaction does not occur, while if it exceeds 1250 ° C, the Si layer deposited on the surface of the steel sheet is dissolved,
It is preferably in the range of 1050 to 1250 ° C.

As described above, the steel sheet used as a raw material (original plate) in the method of the present invention is generally a plain steel sheet or a non-oriented or oriented silicon having a relatively low Si content (usually Si: 4 wt% or less). It is a steel plate. The components of such a steel sheet are not particularly limited, but are preferably specified as follows in order to obtain excellent magnetic properties.

First, the non-metallic element will be described. C: C lowers the initial permeability and the maximum permeability, increases Hc, and increases iron loss. This effect is known to be significant above 0.01 wt% and therefore
C is preferably 0.01 wt% or less. However,
0.01 wt% C at the steelmaking stage for the purpose of improving crystal orientation
%, It is possible to roll, but in this case, it is preferable to carry out decarburization annealing in order to prevent aging and characteristic deterioration, and to make C 0.01 wt% or less. That is, the C concentration may be adjusted at the smelting stage or by performing decarburizing annealing.

O: O is known as an element which enhances iron loss and, when present as colloidal fine particles such as SiO ₂ , significantly deteriorates magnetic properties. O is C
The magnetic characteristics are changed depending on the degree of coexistence with. In particular, it is also known that the iron loss value becomes the minimum when the O content and the C content are substantially equal to each other, and the O content is 0.01 wt% or less like the appropriate range of the C content. It is preferable that

N and S: Since both cause aging, it is preferable to reduce them as much as possible.
It is preferable that the content be 01 wt% or less. P: P has the effect of reducing magnetic deterioration due to oxygen and reducing iron loss, and can be added in a small amount for the purpose of improving the maximum magnetic permeability and the magnetic flux density. Is up to about 1 wt%. H: Since H makes the steel sheet extremely brittle, aggressive inclusion such as H under high pressure should be avoided (usually p
pm level). As described above, it is preferable to minimize C, O, N, S, etc., and optimize the ratio of C and O for the nonmetallic elements.

Next, the metal element will be described. Mn: M in consideration of the improvement of the ductility during hot rolling, and the effect of improving the desulfurization and magnetism in the ordered-disordered transformation.
n is preferably added in a range of 0.5 wt% or less. Ca: If Ca is contained in a large amount, the magnetic permeability is reduced. Therefore, the content is preferably not more than 0.3 wt%.

V: Hc by adding a little V
Are known to be improved. That is, V is 0.
Addition of about 05 wt% promotes the development of crystal grains and improves magnetism. Therefore, V is 0.1 wt
% Can be added up to the upper limit. By adding about 0.05 wt% of Ti, the same effect as V can be expected, so that 0.1 wt% can be added as an upper limit. Be, As: A slight magnetic property improving effect can be expected, and 0.1 wt% of each can be added as an upper limit.

Cu: Up to about 0.7 wt%, the magnetism is not significantly deteriorated, but if it exceeds 0.7 wt%, iron loss increases. Therefore, Cu is 0.7 wt.
% Or less, preferably 0.1 wt% or less. Cr: tends to increase iron loss, and is preferably set to 0.03 wt% or less. Ni: To significantly deteriorate magnetic properties, it is preferable to reduce the Ni as much as possible, and it is preferable to set the content to 0.01 wt% or less.

Al: In the conventional silicon steel sheet, the effect of increasing the electric resistance of Al and the effect of improving ductility are utilized to obtain Si.
The part of Al is replaced with Al. For example,
Instead of 4 wt% Si, 3 wt% of Si and 1 wt% of Al have been considered to maintain the workability. According to the method of the present invention, since the Si content can be 6.5 wt% or more, it is not necessary to newly add Al for improving the magnetic properties. It is preferable that the content be 0.5 wt% or less.

Further, the diffusion process of Si is performed by Ar, He, H ₂
In the case of performing the treatment in a non-oxidizing atmosphere such as the above, there is no particular problem even if Al is contained in the above amount. However,
When processing is performed in an atmosphere containing N ₂ , Al is nitrided due to high temperature processing, and when cooling conditions are not appropriate,
During the cooling process, AlN harmful to the magnetic properties is deposited. Therefore, when the treatment is performed in an atmosphere containing N ₂ , from the viewpoint of minimizing the precipitation of AlN, the Al content is preferably 80 ppm or less.

[0026]

[Example] [Example 1] By the manufacturing line shown in FIG.
No. of Table 1 Silicone tetrachloride gas was used under the conditions shown in Table 2 on a 3.0% Si steel plate having a plate thickness of 0.1 mm and a plate width of 100 to 800 mm having the chemical composition of 1 under the conditions of the siliconized region (reactor furnace length). ) Was continuously treated to produce 6.5% Si steel sheet, and the quality of the obtained steel sheet was evaluated.

FIG. 7 shows the results, in which the horizontal axis shows the plate width and the vertical axis shows the length of the siliconized region (furnace length). The plate shape is evaluated by placing the steel plate on a flat surface, pressing the steel plate against the flat surface at two points in the plate width direction with two pins parallel to the plate width direction at intervals of 30 mm, and between the two pins. The gap between the flat surface and the steel plate was measured. When the maximum value of the gap measured in the plate width direction is y, y ≦ 0.2m
◎ for m, ○ for 0.2 mm <y ≤ 0.4 mm, y> 0.4 mm
The case was evaluated as x.

From the results of FIG. 7, it is understood that the plate shape is very good as long as it is at least the minimum siliconized region length L ₁ defined by the above equation (1) shown by the solid line. Therefore, for example, a plate thickness of 0.1 mm and a plate width of 600 mm is 3.0%.
6.5% Si with good shape after continuous Si-SiC treatment
When manufacturing a steel sheet, it is necessary to perform the treatment in a siliconizing treatment reactor having a furnace length of 3.5 m or more.

[Embodiment 2] With the production line shown in FIG. Board thickness 0.1m with 2 chemical components
3. A 3.2% grain oriented silicon steel sheet having a width of 100 to 600 mm and a width of 100 to 600 mm was subjected to continuous siliconizing treatment under the conditions shown in Table 3 by using silicon tetrachloride gas and changing the siliconized region length. A 5% Si steel plate was manufactured and the quality of the obtained steel plate was evaluated. FIG. 8 shows the results, in which the horizontal axis shows the plate width and the vertical axis shows the length of the siliconized region (reactor length). The plate shape was evaluated in the same manner as in Example 1 above.

From the results shown in the figure, if the minimum siliconizing region length L ₁ defined by the above equation (1) indicated by the solid line is not less than L _{1, the} grain-oriented silicon steel sheet can be formed into a good shape by continuous siliconizing treatment. It turns out that a steel plate can be obtained. Therefore, for example, the plate thickness of 0.1 mm and the plate width of 600 mm may be 3.
3. A 2% grain-oriented silicon steel sheet was subjected to continuous siliconizing treatment to obtain a good shape.
When manufacturing a 5% Si steel sheet, it is necessary to perform the treatment in a siliconizing treatment reactor having a furnace length of 1.3 m or more.

[Embodiment 3] With the production line shown in FIG. Plate thickness 0.3m with 1 chemical composition
m, and a 3.0% Si steel plate having a plate width of 100 to 800 mm was subjected to continuous siliconizing treatment while changing the siliconizing region length using silicon tetrachloride gas, and a 6.5% Si steel plate was manufactured and obtained. The quality of the shape of the steel sheet was evaluated. FIG. 9 shows the results, in which the horizontal axis shows the plate width and the vertical axis shows the length of the siliconized region (reactor length). The plate shape was evaluated in the same manner as in Example 1 above.

From the results shown in the figure, it can be seen that the plate shape is very good as long as it is at least the minimum siliconized region length L ₁ defined by the above equation (1) shown by the solid line. Therefore, for example, a plate thickness of 0.3 mm and a plate width of 600 mm is 3.0%.
6.5% Si with good shape after continuous Si-SiC treatment
When manufacturing a steel sheet, it is necessary to perform the treatment in a siliconizing treatment reactor having a furnace length of 0.7 m or more.

[0033]

According to the present invention described above, a silicon steel sheet having a good plate shape can be manufactured by continuously silicifying the steel sheet in a continuous line.

[Brief description of drawings]

FIG. 1 is a perspective view showing a slit nozzle in a reaction furnace.

FIG. 2 is an explanatory diagram showing an arrangement state of slit nozzles in a reaction furnace.

FIG. 3 is an explanatory diagram showing a Si concentration distribution in a longitudinal direction of a siliconizing treatment reaction furnace and a steel sheet processed in the furnace.

FIG. 4 is a graph showing a relationship between a nozzle arrangement interval in a reaction furnace and a length of a steel sheet unimpregnated silicon portion.

FIG. 5 is a graph showing the lattice constant of Si steel depending on the amount of Si.

FIG. 6 is an explanatory diagram showing a continuous siliconizing treatment line used in Examples.

FIG. 7 is a graph showing the quality of the shape of the steel sheet manufactured in Example 1 by the relationship between the sheet width and the reactor length.

FIG. 8 is a graph showing the quality of the shape of the steel sheet manufactured in Example 2 by the relationship between the sheet width and the reactor length.

FIG. 9 is a graph showing the quality of the shape of the steel sheet manufactured in Example 3 by the relationship between the sheet width and the reactor length.

[Table 1]

[Table 2]

[Table 3]

Claims (1)

(57) [Claims] 1. A method for producing a silicon steel sheet by subjecting a steel sheet to a siliconizing treatment for infiltrating Si from its surface in a reaction furnace and diffusing this Si in the thickness direction, comprising: A plurality of slit nozzles are vertically arranged at intervals of 1 m or less in the longitudinal direction of the furnace, and the furnace length L satisfies the following formula.
By passing the raw steel sheet through the reaction furnace of (m) and blowing a reaction gas to the raw steel sheet from the slit nozzle,
A method for manufacturing a silicon steel sheet by a continuous line, which comprises subjecting a steel sheet to a siliconizing treatment. [Equation 1]