| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a steel material excellent in toughness of a welded heat affected zone in high heat input welding.SOLUTION: A steel satisfying a given chemical component composition comprises a complex oxide containing REM, Zr, Ti, Al, Ca and S, where an oxide having a circle-equivalent diameter of over 3μm is 5.0 per 1 mmfor the complex oxide, the complex oxide number satisfying the formula (1) is 100/mmfor a complex oxide having a circle-equivalent diameter of 0.1 to 3μm, and the average composition of complex oxides having 0.1 to 3μm satisfying the formula (1) is: AlO: 20% or less, TiO: 3 to 20%, ZrO: 5 to 50%, REM oxide: 5 to 50%, CaO: 5 to 50%, and S: 1 to 15%. Formula (1): 0.008≤(1/d)×{mass%S/(mass%CaO+mass%REMO)}≤0.289, (where d is a circle-equivalent diameter of individual complex oxide and 0.1 to 3μm).</p> |
