| 摘要 |
<p>Disclosed are an extremely thick steel plate and a manufacturing method thereof which is provided to manufacture the extremely thick steel plate satisfying the cross-sectional contraction percentage of 35 or greater when a through-thickness tensile test is conducted on the steel plate, and securing the material properties of 150J or greater when an impact test is conducted on the central part of the steel plate by reheating a slab in the range of 900-1050°C to control the size of a microstructure of the surface of the slab and reducing the through-thickness material variation of a final steel plate. The manufacturing method of the extremely thick steel plate comprises steps of: (a) reheating a slab plate at the slab reheating temperature (SRT) of 950-1050°C; (b) hot-rolling the reheated slab plate at the final delivery temperature (FDT) of 700-800°C; and (c) cooling the hot-rolled slab plate at the finish cooling temperature (FCT) of 350-450°C, wherein the slab plate comprises: 0.02-0.12 wt% of carbon (C); 0.5 wt% or less of silicon (Si): 1.0-2.0 wt% of manganese (Mn); 0.003-0.010 wt% of phosphorus (P); 0.0005-0.010 wt% of sulfur (S); 0.2-1.2 wt% of nickel (Ni); 0.05-0.50 wt% of molybdenum (Mo); 0.015-0.060 wt% of aluminum (Al); 0.2-0.5 wt% of copper (Cu); 0.05 wt% or less of titanium (Ti); and the remainder consisting of Fe and inevitable impurities.</p> |
