Chromium-molybdenum steel plate having excellent creep strength and method for manufacturing same

A method for manufacturing a chromium-molybdenum steel plate having excellent creep strength, the method comprising:

• hot-rolling a steel slab including, by weight:
• 0.11 to 0.15% of C, 0.10% or less (exclusive of 0%) of Si, 0.3 to 0.6% of Mn, 0.010% or less (exclusive of 0%) of S, 0.015% or less (exclusive of 0%) of P, 2.0 to 2.5% of Cr, 0.9 to 1.1% of Mo, 0.65 to 1.0% of V, 0.25% or less (exclusive of 0%) of Ni, 0.20% or less (exclusive of 0%) of Cu, 0.07% or less (exclusive of 0%) of Nb, 0.03% or less (exclusive of 0%) of Ti, 0.015% or less (exclusive of 0%) of N, 0.025% or less (exclusive of 0%) of Al, and 0.002% or less (exclusive of 0%) of B, with a balance of Fe and unavoidable impurities so that a finish rolling temperature is equivalent to or higher than Ar3 to manufacture a hot rolled steel plate, and then cooling the hot rolled steel plate;
• reheating the cooled hot rolled steel plate in a temperature range of 900° C. to 1200° C. for 1 t to 3 t minutes [t (mm) is a thickness of the hot rolled steel plate] to austenitize the steel plate;
• quenching the austenitized hot rolled steel plate to room temperature;
• and
• tempering the quenched hot rolled steel plate in a temperature range of 675 to 800° C. for 30 minutes to 120 minutes.