| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel sheet having a large sheet thickness and excellent in high temperature strength and toughness in a sheet thickness center part and a manufacturing method therefor.SOLUTION: There is provided a manufacturing method for a steel sheet excellent in toughness, having a steel composition containing predetermined components and the balance Fe with inevitable impurities, X represented by the following formula (A) of 0.200 or more, an inverse number of square root of effective crystal grain diameter of 9.0 mmor more and Charpy impact absorption energy of 27 J or more and tensile strength of 515 MPa to 690 MPa (inclusive) at -32°C of the steel sheet after stress relief annealing. X=1.78Al+Ti-3.4 N+346B (A), where Al:mass% of Al, Ti:mass% of Ti and B:mass% of B.SELECTED DRAWING: Figure 2 |
