| 摘要 |
An embodiment of the present invention provides a low strength hot rolled steel sheet with excellent hydrogen induced crack resistance and ultra low temperature toughness, comprising: 0.04-0.07 wt% of C, 0.2-0.3 wt% of Si, 0.5-1.0 wt% of Mn, 0.01 wt% or less of P (excluding 0 wt%), 0.001 wt% or less of S (excluding 0 wt%), 0.02-0.05 wt% of Al, 0.02-0.04 wt% of Nb, 0.005-0.02 wt% of Ti, 0.01 wt% or less of Cr (excluding 0 wt%), 0.01 wt% or less of Mo (excluding 0 wt%), 0.0015-0.003 wt% of Ca, the remaining consisting of Fe and inevitable impurities; and has a microstructure including a pearlite with an average size of 10 μm or less in a ferrite matrix, and has a Vickers hardness value of 140 Hv or more. The composition of the hot rolled steel sheet may satisfy a following condition equation of 300 < (1000C + 100Si + 100Mn) × Nb/Ti + 1000(Cr+Mo) < 500. |
