| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength and high-ductility thick steel plate combining strength with ductility, and a production method thereof.SOLUTION: The high-strength and high-ductility thick steel plate is a ferrite pearlite steel plate having predetermined components and a micro structure composed of: a ferrite area fraction of 80-95% at a 1/4 thickness portion; and a pearlite area fraction of 5-20%at a 1/4 thickness portion. The high-strength and high-ductility thick steel plate is characterized in that: an average aspect ratio of a ferrite particle is 1.0-1.5 at the 1/4 thickness portion; an average particle diameter of the ferrite particle is 5-20 μm at the 1/4 thickness portion; an average dislocation density in the ferrite phase is 7×10/mor less at the 1/4 thickness portion; and a Vickers hardness average value in a portion from a surface of the steel plate to the 1/4 thickness portion, or in a portion from 3/4 thickness portion to a rear face is 80-105% of a Vickers hardness average value in a portion from the 1/4 thickness portion to the 3/4 thickness portion in a test of Vickers hardness at 1 mm pitch.SELECTED DRAWING: None |
