| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel member for high-heat input welding which has excellent toughness after welding even when being subjected to high-heat input welding exceeding 300 kJ/cm. SOLUTION: The steel member is disclosed for high-heat input welding having a composition comprising, by mass, 0.03 to 0.08% C, 0.01 to 0.15% Si and 1.60 to 2.6% Mn, and in which carbon equivalent Ceq lies in the range of 0.33 to 0.45, and in which, regarding the structure of a heat-affected zone in the vicinity of a bond when high heat input welding in which welding input heat exceeds 300 kJ/cm is performed, the size of the old austenite intergranular structure other than grain boundary ferrite precipitated from the old austenite grain boundaries is≤10μm, and also, the area proportion of island martensite is≤2%; wherein, the size of the old austenite intergranular structure denotes the average section length measured by a segment method in the grain boundary structure with an inclination of≥15°measured by EBSD (Electron Backscatter Diffraction). COPYRIGHT: (C)2010,JPO&INPIT
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