JPH05125496A - High silicon steel sheet excellent in magnetic property and mechanical property and prepared by means of si cementation method and its production - Google Patents

Abstract

PURPOSE:To provide a high silicon steel sheet excellent in magnetic properties and mechanical properties and its production by means of Si cementation method. CONSTITUTION:The steel sheet is a high silicon steel sheet which contains, by weight, <=0.01% C, 4-7% Si, 0.001-0.01% N, and <=0.01% Al and in which the amount of the nitrides of Si and Al is regulated to <=5ppm. This steel sheet can be produced by applying hot rolling and cold rolling to a slab of low carbon steel with <=4% Si content, subjecting the resulting steel sheet to siliconizing treatment-diffusion heat treatment, and then performing cooling at a cooling rate of >=25 deg.C/sec through the region from 950 to 900 deg.C and at a cooling rate of >=(T-800)/4( deg.C/sec) with respect to sheet temp. T( deg.C) through the region between 900 and 800 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high silicon steel sheet excellent in magnetic properties and mechanical properties by a Si diffusion infiltration treatment method and a method for producing the same.

[0002]

2. Description of the Related Art A so-called Si diffusion permeation treatment method is known as a method for producing a high silicon steel sheet containing Si: 4 wt% or more. According to this method, a low silicon steel is melted and thinned by rolling, and then a high silicon steel sheet is manufactured by infiltrating Si from the surface. According to this method, a high silicon steel sheet is produced without causing a problem of workability. A silicon steel plate can be obtained. The production of high silicon steel sheets by this diffusion infiltration treatment method is generally performed by using ordinary steel sheets or low silicon steel sheets (usually Si: 4 wt.
% Or less) is subjected to Si infiltration treatment (siliconizing treatment) in a mixed gas atmosphere of Si compound such as SiCl ₄ and N ₂ to infiltrate Si from the surface of the steel sheet, and then Si compound is not included. Diffusion heat treatment is applied to the steel sheet in the atmosphere,
The infiltrated Si is diffused in the steel sheet to obtain a high-silicon steel sheet in which Si is uniformly contained.

[0003]

However, in the manufacturing process of such a high silicon steel sheet, Si and A contained in steel are contained.
There is a problem that l is nitrided and this precipitate deteriorates the magnetic properties of the steel sheet. Such a problem of deterioration of magnetic properties due to nitrides is also known in a conventionally manufactured Si: 4 wt% or less silicon steel sheet, but in a high silicon steel sheet having an Si content of 4 wt% or less, Si: The problem of nitriding during heat treatment is particularly significant compared to steel sheets of 4 wt% or less.
The i diffusion diffusion treatment method has a problem that nitriding is more likely to occur because the surface of the steel sheet is activated unlike ordinary annealing.

However, with respect to the conventional Si diffusion and infiltration treatment method, there have been no concrete studies on the nitrides of Si and Al generated during the treatment, the relationship between the nitride and the magnetic characteristics, and the method of suppressing the generation thereof. ..

It is generally known that magnetic steel sheets containing Si and Al deteriorate in magnetic properties due to nitrogen absorption and internal oxidation during coil annealing after hot rolling. As a countermeasure against this, conventionally, Ar or the like is used in an annealing atmosphere. Technology of using an inert gas for increasing the dew point of the annealing atmosphere and making the atmosphere weakly oxidizing Technology for adding elements such as Sb and Sn that act as nitriding inhibitors to the raw material steel (Japanese Patent Publication No. 58-31366) ) acting on the coil surface before annealing the hot-rolled coil as a negative medium of the NH ₃ synthesizing Se, Te, technology to be coated with compounds such as Sb (Japanese Patent Publication No. 62-24506, JP-1-14
No. 2029, JP-A-3-36242) and the like are known.

However, all of the above-mentioned techniques relate to ordinary electromagnetic steel sheets containing Si in an amount of 4 wt% or less, and sufficient effects cannot be obtained for high-silicon steel sheets targeted by the present invention. .. This is due to the Si
This is because the problem of nitriding is particularly remarkable in a high silicon steel sheet whose amount exceeds 4 wt%, and the surface of the steel sheet becomes active in the diffusion and infiltration treatment method, so that nitriding is more likely to occur.

Further, among the above-mentioned conventional techniques, the method (1) has a drawback that the cost is increased due to the increase of additional elements and steps. Further, when the method (1) is applied to the diffusion and infiltration treatment, there is a problem that oxidation occurs, the siliconizing reaction does not proceed, and the surface of the steel sheet becomes dirty, which is not preferable.

Further, according to the studies made by the present inventors, particularly in the production of a high silicon steel sheet by the diffusion and infiltration treatment method, nitrides are likely to precipitate during cooling after the treatment, which results in a decrease in magnetic properties and mechanical properties. It turned out to have an adverse effect.

The present invention has been made in view of the above problems, and relates to a high silicon steel sheet manufactured by a diffusion infiltration treatment method, clarifies the relationship between the amount of nitride and magnetic characteristics and mechanical characteristics, and is excellent in these characteristics. It is a first object to provide a high silicon steel sheet having the above properties. A second object of the present invention is to provide a method capable of appropriately preventing nitriding of Si or Al in the manufacturing process and easily manufacturing the high silicon steel sheet.

[0010]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made a relationship between the amount of nitrides and magnetic properties and mechanical properties of a high silicon steel sheet produced by a diffusion infiltration treatment method, and further,
As a result of studying a method capable of effectively preventing nitriding of i and Al, it is possible to obtain excellent magnetic characteristics and mechanical characteristics by setting the amount of nitrides of Si and Al after Si diffusion and penetration treatment to 5 ppm or less. Further, in the production of such a high silicon steel sheet, nitriding of Si and Al can be prevented by appropriately controlling the cooling rate at the time of cooling the thin plate after the Si diffusion and infiltration treatment, and the amount of these nitrides is 5 ppm or less. It was found that the high silicon steel sheet of The present invention was made on the basis of the above findings, and its constitution is as follows.

(1) C: 0.01 wt% or less, Si:
4-7 wt%, N: 0.001-0.01 wt%, A
1: A high silicon steel sheet containing 0.01 wt% or less and having an amount of Si and Al nitrides of 5 ppm or less and manufactured by a Si diffusion infiltration treatment method having excellent magnetic properties and mechanical properties.

(2) C: 0.01 wt% or less, Si:
4 wt% or less, N: 0.001 to 0.01 wt%, A
l: A low carbon steel slab containing 0.01 wt% or less is hot-rolled and cold-rolled into a thin plate, and then a Si compound and N ₂ are added.
After a siliconizing treatment in a mixed gas atmosphere with and then a diffusion heat treatment for diffusing Si in the plate thickness direction, cooling from 950 ° C to 900 ° C at a cooling rate of 25 ° C / sec or more,
From 900 ℃ to 800 ℃, t ≧ (T-800) / 4
Cooling rate t (° C) that satisfies [T: plate temperature (° C)]
The method for producing a high-silicon steel sheet having excellent magnetic properties and mechanical properties according to the above (1), characterized in that

[0013]

In the steel sheet of the present invention produced by the diffusion and infiltration treatment, the amount of Si and Al nitrides in the steel sheet is limited to 5 ppm or less. This nitride is Si ₃ N ₄ , AlN,
It adversely affects magnetic properties and mechanical properties.

A slab having the chemical composition shown in Table 1 was hot-rolled and cold-rolled by a conventional method to obtain a thin plate having a plate thickness of 0.3 mm. This thin plate is heated to a temperature of 1200 ° C, 10% Si
After charging into a furnace with an atmosphere of Cl ₄ -remainder N ₂ and performing Si infiltration treatment so that the Si amount is enriched to 6.5 wt% on average in the plate thickness direction, followed by diffusion heat treatment at the same temperature 1
During the cooling process from 200 ° C., as shown in FIG.
The cooling rate from 50 ° C. to 800 ° C. was varied by changing the gas jet cooling conditions to 1 to 50 ° C./sec to perform cooling with a cooling pattern, and precipitates were obtained from the obtained high silicon steel sheet by a solvent extraction method. Extraction was performed to identify and quantify the precipitate. As a result of the identification, most of the precipitates were Si ₃ N ₄ , and AlN was partially observed. The concentration of precipitates (Si ₃ N ₄ and AlN) corresponding to each cooling rate is shown in FIG. Further, the precipitates in the steel were observed for these extraction residues using an electron microscope. An enlarged photograph of the precipitate obtained by this observation is shown in FIG.

Further, a ring sample having an inner diameter of 10 mm and an outer diameter of 20 mm and a JIS No. 5 tensile test piece were cut out from each of the above steel plates, and the DC magnetic characteristics and mechanical characteristics were measured. The results are shown in FIGS. 4 and 5. As is clear from these figures, the maximum magnetic permeability and the breaking strength have a high correlation with the precipitate concentration, and the precipitate (Si ₃ N ₄ , AlN) concentration is 5 p
If it is pm or less, excellent properties are exhibited.

Next, the reasons for limiting the composition of the steel sheet will be described. Si: S of the material before the diffusion and penetration treatment due to the problem of rolling workability
The amount of i is 4 wt% or less, and the final amount of Si after the diffusion and penetration treatment is 4 wt% for the purpose of obtaining a high silicon steel sheet.
Is its lower limit, and from the viewpoint of magnetic properties, its upper limit is 7 wt%. Al: When Si is added by the diffusion and permeation treatment method, Al causes the generation of voids that adversely affect the magnetic properties, and therefore it is desirable to reduce it as much as possible. Therefore, the upper limit is 0.01 wt%.

C: The initial permeability and the maximum permeability are lowered, and H
c, an element that increases iron loss, and it is desirable to reduce it as much as possible. However, since the effect can be suppressed by suppressing it to 0.01 wt% or less, 0.01 wt% is the upper limit. N: Since the high-silicon steel sheet of the present invention is made of ordinary silicon steel, its N content is 0.001 to 0.01 wt%.
The range is.

The other elements are preferably specified as follows. O: O is known as an element that enhances iron loss and, when present as colloidal fine particles such as SiO ₂ , significantly deteriorates magnetic properties. Further, O changes the magnetic characteristics depending on the degree of coexistence with C. 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 as in the appropriate range of the C content. It is preferable that

S: Since it causes aging, it is preferable to reduce it as much as possible, preferably 0.01 wt% or less. P: P has a function of reducing magnetic deterioration due to oxygen and reducing iron loss, but when added in a large amount, there is a problem that workability during hot deterioration is deteriorated.
It is preferably set to 2 wt%. In addition, since H makes the steel sheet extremely brittle, it is preferable to avoid aggressive inclusion such as inclusion of H under high pressure (usually below ppm level).

Mn: Mn can be added within a range of 0.5 wt% or less in consideration of the improvement of the spreadability during hot rolling and the effect of improving the desulfurization action and the magnetism in the ordered-disordered transformation. V: It is known that Hc is improved by adding a slight amount of V. That is, by adding an appropriate amount of V, the development of crystal grains is promoted and the magnetism is improved.
Therefore, V can be added with an upper limit of 0.05 wt%.

Ti: By adding a small amount of Ti, the same effect as V can be expected, so that 0.05 wt% can be added up to the upper limit. Ca: When Ca is contained in a large amount, the magnetic permeability decreases, so it is preferably 0.3 wt% or less. 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: Iron loss tends to increase, and it is preferably 0.03 wt% or less. Ni: The magnetic properties are significantly deteriorated, so it is preferable to reduce Ni as much as possible, and it is preferable to set it to 0.01 wt% or less.

Next, a method of manufacturing the above steel sheet will be described. In the production method of the present invention, a low carbon steel slab having Si: 4 wt% or less is hot-rolled or cold-rolled to form a thin plate, and a Si compound (SiCl ₄ , SiH ₄ , SiHCl _3, etc.) is added to the thin plate.
Si: 4 to 7 wt% high silicon steel sheet is manufactured by performing a siliconizing treatment in a mixed gas atmosphere of N and N ₂ to add Si, and then performing a diffusion heat treatment for uniformly diffusing Si in the plate thickness direction. To do. In the production of a high silicon steel sheet by such a siliconizing treatment, nitrides are more likely to be precipitated than in the ordinary annealing in a nitrogen atmosphere.

As described above, the high silicon steel sheet produced by the siliconizing treatment shows excellent magnetic properties and mechanical properties if the precipitate concentration is 5 ppm or less.
As a result of examining the method of suppressing below ppm,
In the cooling process after the siliconizing treatment-diffusion heat treatment, cooling is performed from 950 ° C to 900 ° C at a cooling rate of 25 ° C / sec or more, and from 900 ° C to 800 ° C, t ≧ (T
-800) / 4 [however, T: plate temperature (° C)] is cooled at a cooling rate t (° C) satisfying the precipitate concentration of 5
It has been found that it can be suppressed to below ppm. The reason for the limitation will be described below.

A slab having the chemical composition shown in Table 1 was hot-rolled and cold-rolled according to a conventional method to obtain a thin plate having a plate thickness of 0.3 mm. This thin plate is heated at a furnace temperature of 1200 ° C, 10% SiC
It was charged into a furnace having an atmosphere of l ₄ -balance N ₂ , and was subjected to Si infiltration treatment so that the Si content was enriched to 6.5 wt% on average in the plate thickness direction, and subsequently subjected to diffusion heat treatment at the same temperature. After 1
In the cooling process from 200 ° C., the gas was cooled to various temperatures T (° C.) at a cooling rate of 1 ° C./sec, and then quenched in ice water. The cooling pattern at this time is shown in FIG. The obtained sample was observed for precipitates in steel using an electron microscope. FIG. 7 shows the results of the observations arranged by the quenching start temperature T (quenching start temperature in ice water).

From this result, the quenching start temperature is 950.
Almost no precipitate is observed above ℃, but when the quenching start temperature is 950 ° C. or lower, a needle-shaped precipitate as shown in the electron micrograph of FIG. 8 is observed. As a result of the component analysis by the extraction replica method, most of the needle-shaped precipitates were Si ₃ N ₄ and part of them was Al.
Was identified as N. The above phenomenon is related to the solubility of Si ₃ N ₄ or AlN in steel.
It is considered that Si, Al and N are more stable in the form of precipitates at 50 ° C. or lower.

As described above, it has been found that precipitation of nitrides occurs thermodynamically in the region of 950 ° C. or lower, but the present inventors have found that such precipitation causes diffusion of Si, Al or N in steel. Focusing on the fact that it occurs for the first time, by increasing the cooling rate, S
It was considered that cooling to room temperature would be terminated before i, Al, and N diffused to form a precipitate. In FIG. 9, 12
Various temperature T after Si infiltration treatment-diffusion heat treatment at 00 ° C
The results of observing the precipitates in the steel are shown for the sample obtained by performing the gas jet cooling to (° C.) at a cooling rate of 50 ° C./sec and subsequently cooling it to room temperature at a cooling rate of 1 ° C./sec. The cooling pattern at this time is as shown in FIG. From this result, it can be seen that if the material is rapidly cooled to 800 ° C., no precipitate is formed even at slower temperatures than that.

From the above results, in the temperature range above 950 ° C. and below 800 ° C., no precipitate is formed even when cooled at a slow cooling rate of 1 ° C./sec.
Even in the range of 0 ° C., it was found that precipitates did not deposit if rapidly cooled at a cooling rate of 50 ° C./sec. Furthermore, the present inventors conducted a detailed study on this cooling condition, and
The presence or absence of precipitates was similarly confirmed by varying the cooling rate in the range of 0 ° C to 800 ° C. FIG. 11 shows the cooling pattern at this time, and FIG.
2 shows. Judging from this result, 950 ° C to 800
It can be seen that in the range of ° C, precipitates do not deposit if cooled at a cooling rate of 25 ° C / sec or more. Further, the same precipitates were observed for those cooled in the cooling pattern as shown in FIG. The result is shown in FIG. As a result, cooling from 950 ° C to 850 ° C at 25 ° C / sec,
After that, if you cool up to 800 ℃ at 15 ℃ / sec or more,
It was found that the formation of precipitates was suppressed.

Based on the above results, FIG. 15 shows at what cooling rate cooling is performed in each temperature region to prevent precipitation. According to this 1
When cooling from 200 ° C., if the cooling condition is such that the precipitation region shown in FIG. 15 is passed, Si ₃ N ₄ or Al
N precipitates. On the contrary, if cooling is performed within the solid solution region shown in FIG. 15, the formation of precipitates is suppressed. That is, with respect to the plate temperature T (° C.) during cooling, 1200 ° C. ≧ T> 950 ° C .: cooling rate t> 0
[° C./sec] 950 ° C. ≧ T ≧ 900 ° C .: Cooling rate t ≧ 25 [° C. /
Second] 900 ° C.> T ≧ 800 ° C .: Cooling rate t ≧ (T-80
0) / 4 [° C./sec] 800 ° C.> T ≧ room temperature: cooling rate t> 0 [° C. /
Second], it is possible to suppress the formation of precipitates by cooling at a cooling rate t that satisfies

In the present invention, controlling the cooling rate is an extremely important element. As such a method for controlling the cooling rate, in addition to the gas jet cooling described above, the steel sheet is contacted with a cooled roll. Let
There is a method of adjusting the temperature of the roll and the contact arc length of the steel sheet with respect to the roll.

[0031]

【Example】

Example 1 Table between the slab having a composition of 2 heat rolling, and cold rolling to a thin plate of thickness 0.3 mm, the thin furnace temperature 1200 ℃, 6% SiCl ₄ - atmosphere balance N ₂ In the furnace of No. 3, the Si was enriched to 4 wt% on average in the plate thickness direction by the diffusion and infiltration treatment method, and subsequently subjected to diffusion heat treatment at the same temperature, and then cooled to room temperature by variously changing the cooling rate,
A high silicon steel plate was manufactured. For these steel sheets, the amount of Si and the amount of nitride deposited were measured by chemical analysis. It was also measured breaking strength TS as AC core loss property (W _10/50) and mechanical properties as magnetic properties. The results are shown in Table 3 together with the cooling rate after the diffusion heat treatment. According to this
According to the method of the present invention, a steel sheet having a cooling rate of 25 ° C./sec or more and a nitride content of 5 ppm or less has excellent magnetic properties and mechanical properties.

Example 2 A slab having the composition shown in Table 4 was hot-rolled and cold-rolled to form a thin plate having a plate thickness of 0.1 mm. The thin plate had a furnace temperature of 1150 ° C. and 15% SiCl ₄ -balance N. Charge the furnace in the atmosphere of No. ₂ and apply S by the diffusion infiltration treatment method.
i was enriched to 6.5% on average in the plate thickness direction, and subsequently subjected to diffusion heat treatment at the same temperature, and then up to 1000 ° C. at 10 ° C. /
Seconds, then blown with a cooling gas to cool to 700 ° C. at various cooling rates, and then N ₂
Allowed to cool in gas. Thus iron loss properties of the resulting steel sheet with a (W _10/400) together with the cooling conditions shown in Table 5. According to this, the cooling rate from 1000 ° C to 700 ° C is 2
Those having a temperature higher than 0 ° C./sec show excellent magnetic properties, and it can be seen that the effect of improving the magnetic properties is obtained by cooling at the cooling rate specified in the present invention.

Example 3 A test was carried out in the case where the present invention was applied to an actual continuous production line. A slab having the composition shown in Table 6 was hot-rolled and cold-rolled to have a plate thickness of 0.1.
_4. A thin plate coil having a thickness of 10 mm was subjected to alkali degreasing, and then passed through a continuous furnace in an atmosphere of a furnace temperature of 1150 ° C., 10% SiCl ₄ -balance N ₂ , and Si was averaged in the plate thickness direction. After enriching to 5 wt%, furnace temperature 1150 ° C
Diffusion heat treatment is performed by passing through the diffusion treatment furnace of No. 3, then cooled to 1000 ° C at a cooling rate of 10 ° C / sec, and then a cooling gas is blown from the vertical direction of the plate surface to a cooling rate of 30 ° C / sec. It was cooled to 500 ° C. and wound into a coil. After coating the coil with an insulating film, the coil was sheared into an Epstein shape by a shearing machine, and the magnetic characteristics were measured as it was. Also, from the above coil, JI
S5 test pieces were cut out by machining and their breaking strengths were measured. For comparison, when cooling after diffusion treatment without cooling gas spraying and cooling as it is (cooling rate was about 10 ° C./sec), coils were manufactured and test pieces were prepared in the same manner. Samples were taken and similar magnetic and mechanical properties were measured.

The above results are shown in Table 7 together with the amount of nitride measured by chemical analysis. According to this, it can be seen that even in an actual production line, it is possible to produce a high silicon steel sheet having excellent magnetic properties and mechanical properties by cooling according to the method of the present invention.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

[Table 7]

[Brief description of drawings]

FIG. 1 is a drawing showing a cooling pattern after siliconizing treatment-diffusion heat treatment, which was taken in a test for investigating the relationship between the amount of nitride in a steel sheet and the cooling rate.

FIG. 2 is a drawing showing the relationship between the cooling rate and the amount of nitride after the siliconizing treatment-diffusion heat treatment.

FIG. 3 is an enlarged photograph of a precipitate extracted from the steel plate obtained in the test relating to FIG. 2 by an electron microscope.

FIG. 4 is a drawing showing the relationship between the amount of nitride in a steel sheet and the maximum magnetic permeability.

FIG. 5 is a drawing showing the relationship between the amount of nitride in a steel sheet and the fracture strength.

FIG. 6 is a drawing showing a cooling pattern adopted in a test for investigating a temperature T at which rapid cooling should be started during cooling after the siliconizing treatment-diffusion heat treatment.

FIG. 7 is a drawing showing the relationship between the quenching start temperature and the amount of nitride in the steel sheet during cooling after the siliconizing treatment-diffusion heat treatment.

8 is an enlarged photograph of a precipitate extracted from the steel plate obtained in the test relating to FIG. 7, taken by an electron microscope.

FIG. 9 is a drawing showing the relationship between the gradual cooling start temperature and the amount of nitride in the steel sheet during cooling after the siliconizing treatment-diffusion heat treatment.

FIG. 10 is a drawing showing a cooling pattern adopted in a test for investigating a temperature at which gradual cooling should be started during cooling after the siliconizing treatment-diffusion heat treatment.

FIG. 11 is a drawing showing a cooling pattern adopted in a test for investigating an appropriate cooling rate from 950 ° C. to 800 ° C. during cooling after the siliconizing treatment-diffusion heat treatment.

FIG. 12 is a drawing showing the relationship between the cooling rate between 950 ° C. and 800 ° C. and the amount of nitride in the steel sheet in the cooling process after the siliconizing treatment-diffusion heat treatment.

FIG. 13 is a drawing showing a cooling pattern adopted in a test for investigating an appropriate cooling rate from 950 ° C. to 800 ° C. during cooling after the siliconizing treatment-diffusion heat treatment.

FIG. 14 is a drawing showing the relationship between the temperature at which the cooling rate is changed from 25 ° C./sec to 15 ° C./sec and the amount of nitride in the steel sheet in the cooling process after the siliconizing treatment-diffusion heat treatment.

FIG. 15 is a drawing showing regions of steel plate temperature and cooling rate at which precipitates are formed in cooling after the siliconizing treatment-diffusion heat treatment.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C23C 10/08 8116-4K H01F 1/14

Claims (2)

[Claims] 1. C: 0.01 wt% or less, Si: 4 to 7
wt%, N: 0.001 to 0.01 wt%, Al: 0.
Contains less than 01 wt% and contains 5 p of Si or Al nitride
A high silicon steel sheet excellent in magnetic properties and mechanical properties produced by a Si diffusion infiltration treatment method of pm or less. 2. C: 0.01 wt% or less, Si: 4 wt
% Or less, N: 0.001 to 0.01 wt%, Al: 0.
Hot rolling a low carbon steel slab containing less than or equal to 01 wt%;
After cold rolling into a thin plate, it is subjected to a siliconizing treatment in a mixed gas atmosphere of a Si compound and N ₂ and then subjected to a diffusion heat treatment for diffusing Si in the plate thickness direction.
900 ℃, cooling up to ℃ at a cooling rate of 25 ℃ / sec or more
After that, up to 800 ° C., t ≧ (T−800) / 4 [however,
T: plate temperature (° C)] is cooled at a cooling rate t (° C) satisfying the above condition, the method for producing a high silicon steel sheet having excellent magnetic properties and mechanical properties according to claim 1.