| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel plate which is excellent in HAZ (heat affected zone) toughness in the case of high heat input welding. SOLUTION: The steel plate excellent in weld heat affected zone toughness has a composition containing C, Si, Mn, Al, Nb, Ti, Ca and N, and further at least one selected from the group consisting of Ni, Cu, Cr and Mo, wherein A value expressed by formula; A=53+104[C]+76[Cu]+109[Cr]+37[Ni]+2422[Nb]+31[Mo] satisfies 125≤A≤200, further, the relation of A/G≥4350 is satisfied between the A and G value expressed by formula; G=[Nb]+5[B], further, the number of Ti-containing nitrides with a circle equivalent diameter of <0.05μm is≥5.0×10<SP>6</SP>pieces/mm<SP>2</SP>, the number of Ti-containing nitrides with a circle equivalent diameter of 0.05 to 1.0μm is≥1.0×10<SP>5</SP>pieces/mm<SP>2</SP>, and the number of Ti-containing nitrides with a circle equivalent diameter of >1.0μm is≤5 pieces/mm<SP>2</SP>. COPYRIGHT: (C)2011,JPO&INPIT |
