| 摘要 |
<p>The present invention relates to an extra thick steel sheet and a method to manufacture the same comprising: a step of re-heating a slab comprising, by wt%, 0.06-0.12% of carbon (C), 0.30-0.60% of silicon (Si), 1.20-1.60% of manganese (Mn), 0.03% or less of phosphorus (P), 0.01% or less of sulfur (S), 0.30 or less of chrome (Cr), 0.01-0.05% of aluminum (Al), 0.20-0.50% of copper (Cu), 0.02-0.05% of niobium (Nb), 0.50-1.0% of nickel (Ni), 0.05-0.15% of molybdenum (Mo), 0.015-0.04% of titanium (Ti), 0.001-0.003% of calcium (Ca), and the remainder consisting of iron (Fe) and inevitable impurities at 1150°C or less, which is a re-heating temperature; a step of hot-rolling the re-heated slab at 750-780°C which is a finishing rolling temperature (FRT); and a step of cooling the hot-rolled slab.</p> |
