| 摘要 |
<p>PURPOSE: A hot rolled steel sheet, a cold steel sheet with high carbon and a production method thereof are provided to secure strength, elongation percentage, and surface property and to eliminate a post-annealing process. CONSTITUTION: The production method of a hot-rolled steel sheet and a cold-rolled steel sheet with high carbon executes the following steps. A rolled steel with high carbon is prepared being composed of 0.3-0.9 weight% of C; less than 0.5 weight% of Si; 0.1-1.5 weight% of Mn; less than 0.05 weight% of P; less than 0.03 weight% of S; one or more element selected from Cr, Ni, and Cu with less than 1.5 weight%; the remaining weight% of Fe; and inevitable impurities. A steel sheet is produced executing hot rolling in an austenite region in which the finishing temperature of hot rolling is more than the transformation temperature of Ar3. The steel sheet is rapidly cooled to 520-670 degreeC before starting a phase change in a run-out table[ROT]. A cooling temperature maintained is kept flat. The rolled steel is winded in the cooling temperature maintained.</p> |
