PRESSURE VESSEL STEEL PLATE HAVING EXCELLENT PROPERTY AFTER POST WELD HEAT TREATMENT AND METHOD FOR MANUFACTURING THE SAME

摘要

The present invention relates to a boiler and a pressure vessel of a power plant excellent in PWHT resistance which does not cause a decrease in strength and toughness even when a long post-welding heat treatment (PWHT) is performed, The steel sheet according to any one of claims 1 to 3, which comprises 0.05 to 0.17% of C, 0.50 to 1.00% of Si, 0.3 to 0.8% of Mn, 1.0 to 1.5% of Cr, 0.3 to 1.0% of Mo, 0.003 to 0.30% 0.002 to 0.03% of V, 0.002 to 0.03% of V, 0.002 to 0.03% of Co, 0.003 to 0.30% of Cu, 0.005 to 0.06% of Sol. 0.15%, and the remainder contains Fe and unavoidable impurities, and the PWHT resistance composed of a mixed structure of tempered martensite and residual bainite having a center microstructure of steel sheet of 20% or more by area To an excellent pressure vessel steel plate and a manufacturing method thereof.