| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a steel sheet for a welding structure, which improves toughness at a HAZ by uniformizing a distribution of a precipitated quantity of VN in a HAZ structure formed by high-heat-input welding. SOLUTION: An ingot includes, by mass%, 0.03 to 0.18% C, Si:≤0.5%, 0.4 to 2.0% Mn, P:≤0.02%, S:≤0.02%, 0.005 to 0.04% Al, 0.005 to 0.05% V, 0.0005 to 0.003% Ca, 0.0015 to 0.006% N, and 0.0005 to 0.006% O; and includes inclusion particles having a circle-equivalent diameter of 0.005 to 2.0μm in the number of 100 to 5,000 pieces/mm<SP>2</SP>by number density per unit area, of which the composition includes elements of at least Ca, Al and O, of which a Ca content is 5% or more and an Al content is 5% or more. The manufacturing method comprises the steps of: preparing the above ingot; heating the ingot to 1,200°C or higher and holding it at the temperature for 60 minutes to 300 minutes; and rolling it. COPYRIGHT: (C)2008,JPO&INPIT
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