| 摘要 |
PROBLEM TO BE SOLVED: To provide low C-Mn based steel with super fine grain superior in strength-toughness balance and uniform ductility, or low C-Mn based steel with super fine grain superior in strength-toughness balance, uniform ductility, and ductility. SOLUTION: A method for providing the low C-Mn based steel with super fine grain superior in the strength-toughness balance and uniform ductility includes, adjusting a chemical composition of the steel to satisfy 0.03-0.25% C, 1.0-3.0% Mn by mass%, adjusting a mean grain size ofαto be 3.0μm or less, a mean grain size ofα' to be 10.0μm or less, and a volume percentage ofα' to be 15-23%. A method for obtaining the low C-Mn based steel with super fine grain superior in the strength-toughness balance, uniform ductility, and ductility, includes adjusting especially the mean grain size of the aboveα' to be 5.0μm or less.
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