Pressure vessel steel sheet having excellent PWHT resistance, and manufacturing method therefor
AssigneePosco
InventorSoon-Taik Hong
Life of this patent
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Abstract
Disclosed are a pressure vessel steel sheet and a method for manufacturing the same, the steel sheet comprising: by wt %, 0.10-0.20% of C, 0.15-0.40% of Si, 1.15-1.50% of Mn, 0.45-0.60% of Mo, 0.03-0.30% of Cu, 0.025% or less of P, 0.025% or less of S and 0.005-0.06% of sol. Al; two or more selected from the group consisting of 0.03-0.30% of Cr, 0.002-0.025% of Nb and 0.002-0.025% of Zr, and the balance of Fe and inevitable impurities, wherein the structure comprises a mixture structure of ferrite, perlite and tempered bainite after post weld heat treatment (PWHT) for 60 hours at 600-660° C., and the area fraction of the tempered bainite is at least 10% (excluding 100%).
Claims4
A pressure vessel steel sheet, comprising:
- by wt %, 0.10 to 0.20% of C, 0.15 to 0.40% of Si, 1.15 to 1.50% of Mn, 0.45 to 0.60% of Mo, 0.03 to 0.30% of Cu, 0.025% or less of P, 0.025% or less of S and 0.005 to 0.06% of sol. Al, 0.002 to 0.025% of Zr, one or more selected from the group consisting of 0.03 to 0.30% of Cr and 0.002 to 0.025% of Nb, and the balance of Fe and inevitable impurities,
- wherein the structure comprises a mixture structure of ferrite, perlite and tempered bainite after a post weld heat treatment for a maximum of 60 hours at 600 to 660° C., and an area fraction of the tempered bainite is 10% or higher, excluding 100%,
- wherein a MX precipitate of a size of 10 to 100 nm, where M is one of Cr, Nb, and Zr, and X is one or more of N and C, is present in a crystal grain of the mixture structure, and 0.005 to 0.20% of the MX precipitate is included by a volume fraction.
Dependencies are inferred from the claim text.