| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel which can give a complicated shape in good productivity through several steps of plastic deformation processes, and to provide manufacturing conditions therefor. SOLUTION: This method comprises hot rolling a steel slab composing of 0.01-0.30% C, 2.0% or less Si, 0.10-2.0% Mn, 0.01-0.15% Al, N<=0.008%, O<=0.0100%, S<=0.015%, P<=0.050%, by mass%, and Fe and inevitable impurities as the balance and satisfying the following formula (1), then cooling it to 800-720 deg.C within 5s, furthermore keeping at 720-600 deg.C on a run out at least for 2s, and winding up to make a steel strip or a steel tube; 0.10<=τ<=0.55 (1), whereinτ=(750-Ac1)/(Ac3-Ac1); reverse transformation rate parameter.
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