| 摘要 |
PURPOSE: A very thick steel sheet having a center portion with excellent material properties for a pressure vessel is provided to increase properties of a center portion by applying enough rolling reduction to the center portion. CONSTITUTION: A very thick steel sheet having a center portion with excellent material properties contains C 0.1~0.3wt%, Si 0.1~1.0wt.%, Mn 0.5~2.0wt.%, less than 0.020wt% P, less than 0.005wt% S, Al 0.005~0.1wt%, residual Fe, and inevitable impurities. The thickness of the steel sheet is t, and the tensile strength from a spot of t/4 of the steel sheet to 3t/4 is more than 400MPa. Charpy impact absorption energy at 0°C is more than 80J. A reduction ratio of a tensile area of a thickness direction is more than 30%.
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