| 摘要 |
PROBLEM TO BE SOLVED: To provide a high tensile hot rolled steel plate excellent in high strength and workability, particularly a bore-expanding workability. SOLUTION: A steel blank having a composition containing, by wt.%, 0.03-0.30% C, 0.03-0.30% Ti and satisfying Ti>=(0.0026/C)+0.02 (wherein, Ti, C: contents (wt.%) of the respective elements) is rough rolled in a dynamic recrystallization low temperature zone, and finish rolling is executed in such a way that, after executing reheating to a temperature in the range of 900-1000 deg.C, 4 or more rolling reduction passes in the dynamic recrystallizion low temperature zone are executed to make the finish rolling draft in the dynamic recrystallizion low temperature zone 15-30%, and further, make roll finishing draft temperature(FDT) range of (Ar3 transformation point +30 deg.C) to (Ar3 transformation point +100 deg.C) and, after completing this finish rolling, this rolled steel is rapidly cooled and coiled to make a superfine grain structure in the rolled steel.
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