| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength thick steel plate for structural purpose with a plate thickness of≥50 mm having excellent brittle crack propagation arrest properties, and used for a large structures such as a vessel, and to provide a method for producing the high strength thick steel plate. SOLUTION: The steel plate has a texture where the X-ray intensity ratio in the (211) plane at the rolling face in the central part of the plate thickness is≥1.3, and also, the X-ray intensity ratio in the (100) plane at the rolling face in the 1/4 part of the plate thickness is≥1.5, and the X-ray intensity ratio in the (100) plane at the rolling face in the surface layer part of the plate is≥1.5, and has a steel composition containing, by weight, 0.03 to 0.20% C, 0.03 to 0.5% Si, 0.5 to 2.0% Mn, 0.005 to 0.08% Al and≤0.0050% N. Regarding the method for producing the same, a steel stock is heated at 900 to 1,200°C, is subjected to hot rolling in such a manner that the cumulative draft is controlled to≥30% at a temperate of an Ar<SB>3</SB>point+40°C or above in the central part of the plate thickness, and is controlled to≥30% in the temperature range of an Ar<SB>3</SB>point to an Ar<SB>3</SB>point+<40°C in the central part of the plate thickness, and also, the average pass draft is controlled to≤7%, and is thereafter cooled. COPYRIGHT: (C)2008,JPO&INPIT
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