| 摘要 |
A high strength steel having excellent resistance to brittle crack initiation of a welded part comprises: 0.05-0.10 wt% of C, 1.0-2.5 wt% of Mn, 0.5-1.5 wt% of Si, 0.005-0.10 wt% of Nb, 0.005-0.1 wt% of Ti, and the remaining consisting of Fe and inevitable impurities. A fine structure of a base metal includes acicular ferrite or granular bainite as a matrix. A fine structure of a welding heat influencing part includes, by area fraction, martensitic islands of 2% or lower and retained austenite of 2-10%. Also, the high strength steel has a yield strength of 400 MPa or greater. |
