Pressure vessel steel having excellent hydrogen induced cracking resistance, and manufacturing method therefor

A steel plate for a pressure vessel, the steel plate comprising, by wt %:

• 0.23 to 0.3% of carbon (C),
• 0.05 to 0.50% of silicon (Si),
• 0.03% or less of Mn (Mn),
• 0.005 to 0.1% of aluminum (Al),
• 0.010% or less of phosphorus (P),
• 0.0015% or less of sulfur(S),
• 0.001 to 0.03% of niobium (Nb),
• 0.001 to 0.03% of vanadium (V),
• 0.001 to 0.03% of titanium (Ti),
• 0.01 to 0.20% of chromium (Cr),
• 0.01 to 0.15% of molybdenum (Mo),
• 0.01 to 0.50% of copper (Cu),
• 0.05 to 0.50% of nickel (Ni),
• 0.0005 to 0.0040% of calcium (Ca), and
• a balance of Fe and other unavoidable impurities,
• wherein the steel plate has a microstructure consisting of, in an area fraction, 70% or more of ferrite and a balance of pearlite,
• wherein an average ferrite grain size is 5 to 9.1 μm,
• wherein a maximum concentration of Mn at a central portion of the steel plate is 0.05 wt % or less, and
• wherein the central portion refers to a region occupying ±5% of a total thickness of the steel plate at ½t, where t is a thickness of the steel plate.