| 摘要 |
<p>Provided is a steel material for high heat input welding having a yield stress of 460MPa or more which exhibits excellent toughness in a weld zone even when high heat input welding with a welding heat input quantity exceeding 300 kJ/cm is applied. To be more specific, the high heat input welding steel material has the composition which contains by mass% 0.03 to 0.08% C, 0.01 to 0.15% Si, 1.8 to 2.6% Mn, 0.012% or less P, 0.0005 to 0.0040% S, 0.005 to 0.1% Al, 0.003 to 0.03% Nb, 0.003 to 0.03% Ti, 0.0025 to 0.0070% N and 0.0003 to 0.0025% B, wherein a carbon equivalent C eq falls within a range of 0.33 to 0.45, and martensite islands in the structure of a heat affected zone in the vicinity of a bond when high heat input welding whose welding heat input quantity exceeds 300 kJ/cm is applied is 1vol% or less.</p> |
