| 摘要 |
PROBLEM TO BE SOLVED: To provide a not less than 50 mm-thick thick steel plate excellent in long brittle crack propagation stop property, a method of producing the same, a method of evaluating long brittle crack propagation stop performance, and a testing instrument.SOLUTION: The thick steel plate has an apex shape of a long brittle crack stop part in which a specific region of the center part of a plate thickness is formed with a recessed part in a propagating direction of a long brittle crack at least by a length of the plate thickness from the surface of the steel plate to the specific region of the plate thickness, and the specific region of the center part of the plate thickness has a specific texture. Steel with a specific component is heated, rolled at a steel plate surface temperature of 1,000-850°C and a cumulative rolling reduction ratio of not less than 10%, and thereafter rolled in the state of a specific surface temperature and inner temperature at a 1-pass rolling reduction ratio of not less than 7%, a cumulative rolling reduction ratio of not less than 50% and a steel plate surface temperature after rolling of 800-550°C. The propagation stop performance to a long brittle crack having a crack propagation length of not less than 1 m is evaluated by a test piece length or a distance between tab plate ends that is of the testing instrument to which a test piece is attached and of not less than 2.8 times as long as test piece width using a test piece having a test piece width of not less than 2 m. |
