| 摘要 |
<p>Disclosed is a steel material with excellent low temperature toughness after prolonged post-weld heat treatment (PWHT), and high strength by a control process and alloy components; and a method of manufacturing the same. According to the present invention, the method of manufacturing the steel material comprises: (a) a step of re-heating a steel slab, by weight%, 0.15-0.19% of carbon (C), 0.3-0.4% of silicon (Si), 1.0-1.2% of manganese (Mn), 0.02% or less of phosphorus (P), 0.005% or less of sulfur (S), 0.015-0.05% of soluble-aluminum (S-Al), 0.1-0.2% of copper (Cu), 0.01-0.02% of niobium (Nb), 0.0003% or less of boron (B), 0.15-0.25% of nickel (Ni), 0.15-0.25% of chromium (Cr), 0.08% or less of molybdenum (Mo), 0.01-0.02% of titanium (Ti), 0.02-0.03% of vanadium (V), 0.015% or less of tin (Sn), 0.005% or less of nitrogen (N), and the remainder consisting of Fe and inevitable impurities at 1125-1175°C; (b) a step of rolling the re-heated steel material at a rolling termination temperature of 900-960°C; (c) a step of cooling the rolled steel material; and (d) a step of normalizing the cooled steel material at 840-940°C.</p> |
