JP2015183249A - High tensile thick steel sheet having high young's modulus in rolling direction on steel sheet surface and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel sheet having tensile strength of 780 MPa or more and high Young's modulus in a rolling direction on a steel sheet surface, and a manufacturing method therefor.SOLUTION: There is provided a steel sheet having a component composition containing, by mass%, C:0.06 to 0.25%, Si:0.01 to 0.8%, Mn:0.5 to 2%, P, S, Al:0.005 to 0.1%, N:0.0005 to 0.008% and one or more kind selected from Mo:0.01 to 1%, Nb:0.001 to 0.1%, V:0.001 to 0.5%, Ti:0.001 to 0.1%, and if needed, one or more kind of Cu, Ni, Cr, W, B, Ca and REM and the balance Fe with inevitable impurities and Young modulus in a rolling direction of a steel sheet surface of 220 GPa or more. It is made with a prescribed sheet thickness by hot rolling with determined rolling condition in unrecrystallization region without cooling to the Artransformation temperature or less or after re-heating to the Artransformation temperature or more and re-fired at the Ac1 point or less after cooling from the Artransformation temperature or more at a specific cooling speed.

Description

  The present invention relates to a steel sheet having a thickness of 6 mm or more and a high Young's modulus in the rolling direction on the steel sheet surface and a method for producing the same, and to a material suitable as a high-tensile steel material having a tensile strength of 780 MPa or more.

  In recent years, in the field of steel materials such as construction industrial machinery, tanks, penstock, and line pipes, the strength of steel materials to be used has been directed against the background of increasing the size and weight of structures, and the amount of steel materials used has increased rapidly. Has increased.

  In particular, steel sheets for construction industry machines are being studied to reduce the weight of the structure and reduce energy consumption by reducing the wall thickness by increasing the strength. Decreasing is an issue, and to solve this problem, increasing the Young's modulus is being studied.

  Patent document 1 is one of patent documents relating to improvement of rigidity and Young's modulus of high-strength steel, and describes that a texture is developed by hot rolling in a ferrite + austenite two-phase temperature range. Patent Documents 2, 3, and 4 propose to increase the Young's modulus by developing a texture due to shear deformation during hot rolling in a γ single-phase region for thin steel plates.

JP 2008-13831 A JP 2005-273001 A JP 2008-274395 A JP 2007-291383 A

  The thick steel plate having excellent Young's modulus described in Patent Document 1 is subjected to hot rolling with a cumulative reduction of 50% or more in the ferrite + austenite two-phase temperature range, thereby allowing the (200) plane and (211) in the center of the plate thickness. ) Surface, the X-ray diffraction integration density of (110) plane at 1 mm below the surface is increased, and any one of {100} plane, {211} plane, {110} plane, {111} plane is rolled This is a technique for improving the Young's modulus by setting the average major axis length of ferrite grain colonies aligned within 5 ° to the surface to 60 μm or less at the center of the plate thickness and 30 μm or less at 1 mm below the surface.

  However, in the method described in Patent Document 1, the target tensile strength level is as low as 600 MPa class, and in order to increase the Young's modulus, the ferrite phase fraction is ensured and the ferrite phase is developed to develop a working texture. + Because of the need for strong processing in the austenite two-phase temperature range, there were problems in production stability and the like.

  Patent Documents 2, 3, and 4 develop a texture of {110} <223> and {110} <111> orientations by shearing the steel sheet surface during hot rolling in the austenite single phase region. This is a technique for increasing the Young's modulus in the rolling direction. However, all of them are intended for thin steel plates and are manufactured by specifying the friction coefficient, effective strain amount and rolling reduction ratio of the rolling rolls and steel plates in the rolling stand, and cannot be applied to thick steel plates.

  The present invention has been made in view of such circumstances, and is a high-tensile steel plate having a plate thickness of 6 mm or more, a tensile strength of 780 MPa or more, and a Young's modulus in the rolling direction on the steel plate surface of 220 GPa or more. It aims at providing the manufacturing method.

As a result of intensive studies on increasing the Young's modulus in the rolling direction on the steel sheet surface, the present inventors have obtained the following knowledge.
(1) In order to increase the Young's modulus in the rolling direction on the steel sheet surface, it is effective to develop {110} <111> and {112} <111> textures on the steel sheet surface.
(2) For that purpose, it is necessary to properly define the pass reduction rate, the inter-pass time, and the cumulative reduction rate in the non-recrystallization temperature range from the steel plate surface to 1/2 position of the plate thickness.
(3) When the tensile strength is set to 780 MPa or more, the steel having a specific component composition is hot-rolled and then cooled from the Ar3 transformation point or higher to 400 ° C or lower at a cooling rate of 10 ° C / s or higher to properly define the tempering temperature. Tempering is required.
(4) Moreover, when the heating apparatus installed on the same production line as a rolling mill and a cooling device is used, the tempering process time is shortened, and a short delivery time is possible.

The present invention has been made based on further findings based on the obtained knowledge.
1. Component composition is mass%, C: 0.06-0.25%, Si: 0.01-0.8%, Mn: 0.5-2%, P: 0.015% or less, S: 0 0.005% or less, Al: 0.005-0.1%, N: 0.0005-0.008%, Mo: 0.01-1%, Nb: 0.001-0.1%, V: One or more of 0.001 to 0.5%, Ti: 0.001 to 0.1% is contained, the balance is made of Fe and inevitable impurities, and the Young's modulus in the steel sheet surface rolling direction is 220 GPa or more. A high-tensile thick steel plate having a high Young's modulus in the rolling direction on the surface of the steel plate.
2. Component composition is mass%, C: 0.06-0.25%, Si: 0.01-0.8%, Mn: 0.5-2%, P: 0.015% or less, S: 0 0.005% or less, Al: 0.005-0.1%, N: 0.0005-0.008%, Mo: 0.01-1%, Nb: 0.001-0.1%, V: 0.001 to 0.5%, Ti: 0.001 to 0.1% of one type or two or more types, the balance is made of Fe and inevitable impurities, the old γ particle size is 15 to 40 μm, Further, the degree of accumulation of {110} <111> and {112} <111> texture on the steel sheet surface is 3 or more, and the Young's modulus in the steel sheet surface rolling direction is 220 GPa or more. High tensile steel plate with high rate.
3. Furthermore, the component composition contains 1% or 2 or more of Cu: 2% or less, Ni: 4% or less, Cr: 2% or less, W: 2% or less in mass% 1 or A high-tensile thick steel plate having a high Young's modulus in the rolling direction on the surface of the steel plate according to 2.
4). Furthermore, the component composition contains one or more of B: 0.0003 to 0.003%, Ca: 0.01% or less, REM: 0.02% or less in mass%. A high-tensile thick steel plate having a high Young's modulus in the rolling direction on the steel plate surface according to any one of 1 to 3.
After casting the steel having the component composition according to any one of 5.1 to 4, after cooling to the Ar ₃ transformation point or less, or after cooling to the Ar ₃ transformation point or less, re-recover above the Ac ₃ transformation point. Heating is performed, and hot rolling including rolling at a pass reduction rate of 10 to 20% in an unrecrystallized region, an interpass time of 20 seconds or less, and a cumulative reduction rate of 40% or more is performed, and then from the Ar ₃ transformation point or higher. A method for producing a high-tensile thick steel plate having a high Young's modulus in the rolling direction on the surface of the steel sheet, wherein the steel sheet is cooled to a temperature of 400 ° C. or less at a cooling rate of 10 ° C./s or higher and then tempered to the Ac1 point or lower.
After casting the steel having the component composition according to any one of 6.1 to 4 without cooling below the Ar ₃ transformation point or after cooling to the Ar ₃ transformation point or less, re-recover above the Ac ₃ transformation point. Heating to perform hot rolling including rolling with a pass reduction ratio of 10 to 20% in the non-recrystallized region, an interpass time of 20 s or less, and a cumulative reduction ratio of 40% or more, and then the Ar ₃ transformation point or more After cooling to a temperature of 250 ° C. or less at a cooling rate of 10 ° C./s or higher, and using a heating device installed on the same production line as the rolling mill and the cooling device, at an average temperature rising rate of 1 ° C./s or higher. A method for producing a high-tensile thick steel plate having a high Young's modulus in the rolling direction on the surface of the steel plate, characterized by tempering to an Ac1 point or less.

  According to the present invention, the tensile strength has a high strength of 780 MPa or more, the Young's modulus in the rolling direction on the steel plate surface is 220 GPa or more, and a high-tensile thick steel plate having high rigidity can be stably produced at low cost. It is extremely useful in industry.

  The reason for limiting the components of the present invention will be described. In the description,% is mass%.

C: 0.06 to 0.25%
C is an indispensable element for obtaining the strength required for structural steel. However, if contained in a large amount, the amount of martensite produced in the weld heat affected zone increases and the toughness is lowered. 25%. On the other hand, if the content is less than 0.06%, sufficient strength cannot be obtained, and a large amount of alloy elements are required, so that the weldability is lowered. Therefore, the lower limit is made 0.06%. Preferably it is 0.12-0.22%, More preferably, it is 0.12-0.18%.

Si: 0.01 to 0.8%
Si acts as a deoxidizer, and in the present invention, it is necessary to contain 0.01% or more in order to carry out moderate deoxidation, but if it contains more than 0.8%, the base material and the weld heat affected zone While the toughness is significantly reduced, the weldability is significantly reduced. For this reason, the range of Si was 0.01 to 0.8%. Preferably, it is 0.05 to 0.8%.

Mn: 0.5-2%
Mn must be contained in an amount of 0.5% or more from the viewpoint of securing the strength of the base material. On the other hand, if it contains more than 2%, the hardenability is excessively increased and the toughness of the weld heat affected zone is remarkably lowered, so it is necessary to make it 2% or less. Preferably, it is 0.6 to 1.6%.

P: 0.015% or less When P is contained in excess of 0.015%, the toughness of the base metal and the weld heat-affected zone is remarkably reduced, so the content is limited to 0.015% or less.

S: 0.005% or less If S is contained in excess of 0.005%, the toughness of the base metal and the weld heat-affected zone is significantly reduced.

Al: 0.005 to 0.1%
Al needs to contain 0.005% or more in order to fully deoxidize molten steel. On the other hand, if the content is more than 0.1%, the amount of Al dissolved in the base material increases and the base material toughness is reduced, so it is necessary to limit it to 0.1% or less. Preferably, it is 0.01 to 0.06%.

N: 0.0005 to 0.008%
N is contained in order to refine the structure by forming a nitride with Ti or the like and to improve the toughness of the base material and the weld heat affected zone. However, if the content is less than 0.0005%, the effect of refining the structure is not sufficient. On the other hand, if the content exceeds 0.008%, the amount of N dissolved in the base material increases, and the base material toughness is significantly reduced. In addition, coarse carbonitrides are formed also in the weld heat affected zone, and the toughness is lowered. Therefore, it is necessary to limit the range to 0.0005 to 0.008%. Preferably, it is 0.001 to 0.006%.

Mo: 0.01 to 1%, Nb: 0.001 to 0.1%, V: 0.001 to 0.5%, Ti: 0.03% or less, or one or more Mo: 0.01 ~ 1%
Mo is an element effective for increasing the strength of the base material, but if it is less than 0.01%, its effect is insufficient. On the other hand, if it is contained in a large amount, it causes an increase in strength due to precipitation of alloy carbides and decreases toughness. Therefore, the content is made 0.01 to 1%. Preferably, it is 0.2 to 0.8%.

Nb: 0.001 to 0.1%
Nb is an element effective for strengthening steel, and particularly an element that greatly contributes to the development of texture. However, if it is less than 0.001%, the effect is insufficient, and the content exceeding 0.1% is a base material. The toughness of the steel is remarkably reduced, so 0.001 to 0.1%. Preferably it is 0.001 to 0.05%.

V: 0.001 to 0.5%
V is effective in improving the strength and toughness of the base material, and is effective for lowering the solid solution N by being precipitated as VN, but if the content is less than 0.001%, the effect is insufficient, If it contains more than 0.5%, the toughness decreases due to precipitation of hard VC, so 0.001 to 0.5%. Preferably, it is 0.01 to 0.1%.

Ti: 0.03% or less Ti produces TiN at the time of rolling heating or welding, effectively suppressing the coarsening of austenite and improving the toughness of the base material and the weld heat affected zone. However, if the content is more than 0.03%, the Ti nitride becomes coarse and the toughness of the base metal and the weld heat affected zone is lowered, so it is necessary to limit it to 0.03% or less.

  The above is the basic component composition of the present invention, and the balance is Fe and inevitable impurities. In addition to the above basic component composition, the high-tensile steel of the present invention can contain one or more of Cu, Ni, Cr, and W for the purpose of further increasing the strength.

Cu: 2% or less Cu can improve the strength of the steel without impairing the low-temperature toughness, but if it is contained in an amount of more than 2%, it causes cracks on the surface of the steel sheet during hot rolling, so the content is made 2% or less.

Ni: 4% or less Ni is a beneficial element that improves the strength of the steel and the toughness of the weld heat affected zone. However, if the Ni content exceeds 4%, the economy is inferior. Therefore, when it contains Ni, the content shall be 4% or less. Preferably it is 2% or less.

Cr: 2% or less Cr is an element effective for improving strength and toughness. However, if the Cr content exceeds 2%, weldability decreases. Therefore, when it contains Cr, the content is made 2% or less. Preferably, it is 0.1% to 1%.

W: 2% or less W has an effect of improving strength. In order to acquire the effect, it is preferable to contain 0.05% or more. However, if it exceeds 2%, the weldability decreases. Therefore, when it contains W, the content is made 2% or less. Preferably, it is 0.05 to 2%.

  In addition to the above composition, the present invention may contain one or more of B, Ca, and REM for the purpose of further improving the material.

B: 0.0003 to 0.003%
B has the effect of suppressing the ferrite transformation from the grain boundary by segregating at the austenite grain boundary and improving the hardenability, but it is necessary to contain 0.0003% or more in order to fully exhibit this effect. is there. However, if it exceeds 0.003%, it becomes a precipitate and the hardenability is lowered and the toughness is lowered, so the upper limit is made 0.003%. Preferably it is 0.0005 to 0.0020%.

Ca: 0.01% or less Ca is an element indispensable for controlling the form of sulfide inclusions. However, the content exceeding 0.01% causes a decrease in cleanliness. Therefore, in order to control the form of sulfide inclusions, when Ca is contained, the content is limited to 0.01% or less.

REM: 0.02% or less REM also has the effect of improving the quality of the material by forming oxides and sulfides in the steel as in Ca, but the effect is saturated even if it is contained in an amount of more than 0.02%. 0.02% or less.

Next, the reason for limiting the microstructure of the present invention will be described.
[Organization]
In order to set the Young's modulus in the rolling direction on the steel plate surface to 220 GPa or more, the {111} <111> and {112} <111 in which the <111> direction having a high Young's modulus is oriented in the rolling direction as a texture on the surface of the steel plate. > Is set to 3 or more. If the degree of integration is less than 3, the Young's modulus in the rolling direction is less than 220 GPa, and the rigidity of the steel sheet cannot be increased. In the present invention, the surface of a steel plate refers to a region from the plate surface to at least 1/10 plate thickness position (1/10 position of plate thickness) in the plate thickness direction.

[Old γ particle size]
The old γ particle size is set to 15 to 40 μm because if the old γ particle size is less than 15 μm, the hardenability is lowered and sufficient strength cannot be secured, and if the old γ particle size exceeds 40 μm, the toughness is remarkably reduced. It is to do.

  In the present invention, in order to secure desired strength and toughness, the martensite + lower bainite + retained austenite structure fraction is set to 95% or more.

  Next, the reasons for limiting the manufacturing conditions of the present invention will be described. The temperature regulation of the steel sheet in the present invention is the temperature at the center of the sheet thickness, and is obtained by calculation from the surface measured temperature of the steel sheet. Although the average cooling rate and the average temperature rising rate are defined at the center of the plate thickness, the vicinity of the center of the plate thickness has a substantially similar temperature history, and is not limited to the center of the plate thickness.

[Rolling conditions]
Even if the slab is started to be hot-rolled as it is without cooling below the Ar3 transformation point, the hot-rolling may be started after the slab once cooled is reheated above the Ac3 transformation point. If rolling is started in a temperature range where the steel is austenitized, the effectiveness of the present invention is not lost. The present invention is effective for any steel melted by a converter method, an electric furnace method, etc., and any slab produced by a continuous casting, ingot casting method, etc. The manufacturing method is not specified.

  In the hot rolling, one pass is performed in the non-recrystallization temperature range at a pass reduction rate of 10 to 20% and the time between passes is 20 s or less, and the cumulative reduction rate in the non-recrystallization temperature range is 40% or more, and the rolling end temperature Ar3 Above the transformation point. When the pass reduction ratio exceeds 20%, the shear strain introduced in the vicinity of the steel sheet surface during rolling becomes small, and the development of the texture becomes small.

  On the other hand, if the pass reduction ratio is less than 10%, the temperature drop during rolling increases as the number of passes increases, and rolling in the austenite region above the Ar3 transformation point becomes difficult, and the reduction in rolling efficiency increases. The pass reduction rate is 10 to 20%.

  Furthermore, by setting the time between passes to 20 s or less and the cumulative reduction ratio in the non-recrystallized region to 40%, the cumulative effect of shear strain during rolling increases, and a desired texture develops. In the present invention, the hot rolling only needs to include the above-described rolling in the non-recrystallized region, and does not prevent other rolling conditions from being included.

[Cooling conditions]
After hot rolling is completed, forced cooling is performed from a temperature equal to or higher than the Ar3 transformation point to a predetermined cooling stop temperature at a cooling rate of 10 ° C./s or higher in order to secure a base material strength of 780 MPa or higher and increase Young's modulus. The cooling stop temperature is set to 400 ° C. or lower. After the cooling is stopped, the tempering process is performed to 250 ° C. or lower when the heating device installed on the same production line as the rolling mill and the cooling device is used.

  In order to cool, the working texture developed by the shear strain introduced in the non-recrystallized region of austenite is transformed into a base material structure of the desired texture by martensite transformation. Therefore, at least the cooling rate in the austenite region is 10 ° C. In order to complete the transformation from austenite to martensite and strengthen the base material so that the tensile strength is 780 MPa or more, the stop temperature is 400 ° C. or less.

[Tempering]
After cooling, tempering is performed to a temperature of Ac1 point or lower. Tempering has an average heating rate of 1 ° C./s or higher, and the steel plate temperature is heated to Ac1 or lower, thereby suppressing the diffusion of C during heating and producing coarse carbides at the martensitic interface. The carbide size generated between the martensite lath is 100 nm or less, and the toughness is improved.

  The cooling rate to 100 ° C. or less after tempering is 0.05 ° C./s or more and 20 ° C./s or less so as to prevent toughness deterioration due to coarsening of precipitates during cooling. Is desirable.

  The tempering may be performed using a heating device installed directly on the same production line as the rolling mill and the direct quenching device or the accelerated cooling device. The direct connection can shorten the time required from the rolling / quenching process to the tempering process, thereby improving productivity and reducing heat energy. A solenoid type induction heating device can be used as the heating device.

  Next, the usefulness of the present invention will be further explained by examples.

  Steels A to O having chemical components shown in Table 1 were melted and cast into slabs, heated in a heating furnace, and then rolled into a steel plate. After rolling, it was directly quenched and then tempered using an atmosphere furnace and a solenoid induction heating device.

  When a solenoid type induction heating apparatus was used, the average heating rate at the center of the plate thickness was controlled by the plate passing rate of the steel plate. In addition, when hold | maintaining at tempering temperature, it hold | maintained in the range of +/- 5 degreeC by reciprocating and heating a steel plate.

  The cooling after heating was air cooling. The temperature at the center of the plate thickness, such as the tempering temperature and the quenching temperature, was obtained by heat transfer calculation from the temperature measurement results at the surface in succession by a radiation thermometer.

  The tensile test was performed according to JIS Z 2241. Yield strength and tensile strength were measured with a JIS No. 5 test piece when the plate thickness was 20 mm or less, and with a JIS No. 4 test piece taken from 1/4 of the plate thickness when the plate thickness exceeded 20 mm. . The specimen collection direction was the rolling direction.

  The toughness was evaluated by a fracture surface transition temperature (vTrs) obtained by a Charpy impact test using a test piece taken from 1/4 part of the plate thickness after collecting an impact test piece specified in JIS Z 2242. The specimen collection direction was the rolling direction.

  The old γ grain size was evaluated by observing the cross section in the rolling direction of the steel sheet with 10 fields of view with an optical microscope, and evaluating the average value of the equivalent circle diameter of each crystal grain.

  For the texture, from the surface of the steel plate to 1/4 of the plate thickness, specimens were collected every 1 mm in the plate thickness direction on the plane parallel to the plate surface, and (110), (200), (211) positive electrode dot diagrams were measured. Then, using these, a three-dimensional texture was calculated and evaluated by the maximum value of the X-ray random intensity of each crystal orientation in the Φ2 = 45 ° cross section.

  The Young's modulus was measured by a resonance method by collecting a plate-like test piece having a thickness of 2 mm, a width of 10 mm, and a length of 60 mm.

  The target values for each characteristic were a yield stress of 685 MPa or more, a tensile strength of 780 MPa or more, a vTrs of −40 ° C. or less, and a Young's modulus of 220 GPa or more in the rolling direction at a surface of 1 mm.

  Table 2 shows the steel sheet production conditions, the yield strength, tensile strength, fracture surface transition temperature (vTrs), old γ grain size, texture strength from the surface 1 mm to the center of the plate thickness, and Young's modulus. The comparative example whose component composition or manufacturing condition is outside the scope of the present invention is any one of the above target value and the degree of accumulation of the microstructure described above (the degree of accumulation of {110} <111> and {112} <111> is 3 or more). Or I could not satisfy everything.

Claims (6)

  Component composition is mass%, C: 0.06-0.25%, Si: 0.01-0.8%, Mn: 0.5-2%, P: 0.015% or less, S: 0 0.005% or less, Al: 0.005-0.1%, N: 0.0005-0.008%, Mo: 0.01-1%, Nb: 0.001-0.1%, V: One or more of 0.001 to 0.5% and Ti: 0.001 to 0.1% are contained, the balance is made of Fe and inevitable impurities, and the Young's modulus in the rolling direction on the steel sheet surface is 220 GPa. A high-tensile thick steel plate having a high Young's modulus in the steel sheet surface rolling direction.   Component composition is mass%, C: 0.06-0.25%, Si: 0.01-0.8%, Mn: 0.5-2%, P: 0.015% or less, S: 0 0.005% or less, Al: 0.005-0.1%, N: 0.0005-0.008%, Mo: 0.01-1%, Nb: 0.001-0.1%, V: 0.001 to 0.5%, Ti: 0.001 to 0.1% of one type or two or more types, the balance is made of Fe and inevitable impurities, the old γ particle size is 15 to 40 μm, And the accumulation degree of {110} <111> and {112} <111> texture on the steel sheet surface is 3 or more, and the Young's modulus in the steel sheet surface rolling direction is 220 GPa or more. High tensile steel plate with high Young's modulus.   Furthermore, the component composition contains one or two or more of Cu: 2% or less, Ni: 4% or less, Cr: 2% or less, W: 2% or less in mass%. A high-tensile thick steel plate having a high Young's modulus in the rolling direction on the steel plate surface according to 1 or 2.   Furthermore, the component composition contains one or more of B: 0.0003 to 0.003%, Ca: 0.01% or less, REM: 0.02% or less in mass%. The high-tensile thick steel plate having a high Young's modulus in the rolling direction on the steel plate surface according to any one of claims 1 to 3. The steel having the composition according to any one of claims 1 to 4 is cast and then cooled to below the Ar ₃ transformation point, or after cooling to the Ar ₃ transformation point or less, and then returned to the Ac ₃ transformation point or more. Heating is performed, and hot rolling including rolling at a pass reduction rate of 10 to 20% in an unrecrystallized region, an interpass time of 20 seconds or less, and a cumulative reduction rate of 40% or more is performed, and then from the Ar ₃ transformation point or higher. A method for producing a high-tensile thick steel plate having a high Young's modulus in the rolling direction on the surface of the steel sheet, wherein the steel sheet is cooled to a temperature of 400 ° C. or less at a cooling rate of 10 ° C./s or higher and then tempered to the Ac1 point or lower. The steel having the composition according to any one of claims 1 to 4 is cast and then cooled to below the Ar ₃ transformation point, or after cooling to the Ar ₃ transformation point or less, and then returned to the Ac ₃ transformation point or more. Heating to perform hot rolling including rolling with a pass reduction ratio of 10 to 20% in the non-recrystallized region, an interpass time of 20 s or less, and a cumulative reduction ratio of 40% or more, and then the Ar ₃ transformation point or more After cooling to a temperature of 250 ° C. or less at a cooling rate of 10 ° C./s or higher, and using a heating device installed on the same production line as the rolling mill and the cooling device, at an average temperature rising rate of 1 ° C./s or higher. A method for producing a high-tensile thick steel plate having a high Young's modulus in the rolling direction on the surface of the steel plate, characterized by tempering to an Ac1 point or less.