| 摘要 |
PROBLEM TO BE SOLVED: To provide steel which is not only tough, but also has high elongation as-worked or in a state after heating to the temperature region below an Ae1 point after the completion of working, and to provide a production method therefor. SOLUTION: The temperature of a steel member in the process of working is kept lower than an Ae1 point, and working is applied so that a working degree expressed as a reduction of area or a compression rate is≥10%. Thus, steel satisfying the conditions that the recrystallization ratio of the structure at least in the surface layer part is≤20% when the cross section is observed as-worked or in a state after heating to the temperature region below an Ae1 point after the completion of the working is obtained. The recrystallization ratio RR is defined as RR=100×(the area of equi-axed crystals)/(the area of spherical crystals+the area of elongated crystals)(%) in a ferrite band. COPYRIGHT: (C)2004,JPO
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