| 摘要 |
<p>The present invention relates to a steel sheet for a pressure vessel having excellent strength and toughness after post welding heat treatment (PWHT) and a manufacturing method thereof. The steel sheet for a pressure vessel having excellent strength and toughness after PWHT comprises: 0.05 to 0.2 wt% of C, 0.15 to 0.5 wt% of Si, more than 1.6 wt% to 2.0 wt% or less of Mn, 0.030 wt% or less of P, 0.030 wt% or less of S, 0.015 to 0.05 wt% of Al, 0.005 to 0.05 wt% of Cr, 0.005 to 0.1 wt% of Mo, 0.005 to 0.08 wt% of V, 0.001 to 0.05 wt% of Ti, 0.05 to 0.6 wt% of Ni, more than 0.35 wt% to 0.65 wt% or less of Cu, and the remainder consisting of Fe and other inevitable impurities, wherein the steel sheet includes a mixed structure of polygonal ferrite and bainitic ferrite in a pillar form, and has a fine structure including carbonitride including one or more kinds of Cr, Mo, Ti, and V, 0.02 volume% or more. According to the present invention, it is possible to provide a steel sheet for a pressure vessel capable of securing an excellent mechanical property since strength and toughness do not deteriorate even after PWHT for about 50 hours while having a strength of about 600 MPa or higher.</p> |
