| abstract |
A high-strength and highly ductile thick steel plate having both strength and ductility and a method for producing the same are provided. A ferrite pearlite steel sheet having a predetermined component, wherein the ferrite area fraction of the ¼ thickness part of the microstructure is 80 to 95%, and the pearlite area fraction of the ¼ thickness part is 5 to 20%. In the structure formed, the average aspect ratio of the ferrite grain of 1/4 thick part is 1.0 to 1.5, the average particle diameter of the ferrite grain of 1/4 thick part is 5 to 20 μm, and the 1/4 thick part The average dislocation density in the ferrite phase is 7 × 10 12 / m 2 or less, and the Vickers hardness average from the surface of the steel sheet to 1/4 thickness or from 3/4 thickness to the back surface in a 1 mm pitch Vickers hardness test. A high-strength, high-ductile, thick steel plate having a value of 80 to 105% of the average value of Vickers hardness from a ¼ thick part to a ¾ thick part. [Selection figure] None |