Steel Plate

Abstract: This steel plate has a prescribed chemical composition, and the microstructure of the t/4 region, which is the range from 1/8 to 3/8 of the plate thickness in the plate thickness direction from the surface, contains, as the area ratio, less than 10.0% ferrite and more than 90.0% pearlite. The remainder of the microstructure is one or two or more of bainite, martensite, and retained austenite. In this microstructure, the maximum diameter of the granular cementite present on the block boundaries and the granular cementite present on the colony boundaries is not more than 0.50 µm. Of the granular cementite present on block boundaries and the granular cementite present on colony boundaries, the number per unit length on the block boundaries or colony boundaries is at least 0.3/µm and not more than 5.0/µm. This granular cementite is cementite with an aspect ratio of less than 10 and a tensile strength of at least 1200 MPa.

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