| 摘要 |
A steel plate according to the present invention has a predetermined chemical composition and contains specific oxide particles. The oxide particles include constituent elements excluding oxygen in contents, in mass percent, meeting the conditions: 2% < Ti < 40%, 5% < A1 < 30%, 5% < Ca < 40%, 5% < REM < 50%, 2% < Zr < 30%, and 1.5 ‰¤ REM/Zr. Of the oxide particles, those with an equivalent circle diameter of less than 2 µm are present in a number density of 300 or more per square millimeter, and those with an equivalent circle diameter of 2 µm or more are present in a number density of 100 or less per square millimeter. Of titanium nitride particles, those with an equivalent circle diameter of 1 µm or more are present in a number density of 7 or less per square millimeter, and those with an equivalent circle diameter of 20 nm or more are present in a number density of 1.0x 10 6 or more per square millimeter. The steel plate meets a condition specified by the relational expression: |da-df|/da ‰¤ 0.35. |
