| 摘要 |
PURPOSE: A method for manufacturing a bainitic steel with good low temperature toughness is provided, which is characterized in that bainite matrix structure is minutely controlled by accelerated cooling after finishing hot rolling process at high temperatures, thus it is possible to produce a bainitic steel with a tensile strength of 60kgf/mm¬2. CONSTITUTION: The method for manufacturing a bainitic steel with good low temperature toughness includes the steps of reheating a slab comprising C 0.01 to 0.04 wt.%, Mn 1.2 to 2.0 wt.%, Si 0.1 to 0.3 wt.%, Al 0.02 to 0.06 wt.%, Ti 0.01 to 0.03 wt.%, Nb 0.04 to 0.06 wt.%, V 0.05 to 0.07 wt.%, Mo 0.15 to 0.25, B 0.001 to 0.002 wt.%, 0.02 wt.% or less of S, 0.02 wt.% or less of P, N 10 to 100 ppm, O 0.01 to 0.05 wt.%, Ca 10 to 100 ppm, a balance of Fe and incidental impurities in a temperature range of 1050 to 1300°C, followed by hot rolling; finish hot rolling the slab at a temperature higher than Ar3 transformation temperature by 100 to 200 deg.C; accelerated cooling the hot rolled steel sheet at a cooling rate of 7 to 15 deg.C.
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