| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a thick steel plate which is excellent in characteristic of brittle crack propagation arrest. <P>SOLUTION: The thick steel plate has a microstrutcure which includes a ferrite phase as a main phase and one or more kinds of pearlite phase, bainitic phase and martensitic phase as a second phase. The ferrite phase with an average particle diameter of 3 μm or less is formed in at least an area of 10-20% in plate thickness from the front and rear surfaces in the direction of the thick steel plate, and its area ratio to the total quantity of ferrite in the area is 30% or more. Also, it is formed in an area of less than 10% in plate thickness from the front and rear surfaces in the direction of the thick steel plate, and its area ratio to the total quantity of ferrite in the area is less than 30%. Thus, the characteristic in brittle crack propagation arrest can be greatly improved in the thick steel plate. <P>COPYRIGHT: (C)2012,JPO&INPIT |
